C13 and C15 On-highway Engines Caterpillar

Sensor Signal (Analog, Active) - Test

Usage:

C15 B5R

System Operation Description:

This procedure covers the following diagnostic trouble codes:

Show/hide table

Table 1
-2 Diagnostic Trouble Codes for Active Analog Sensors
J1939 Code	Description	Callout in the Illustrations for Component Location	Location of the Connector for the Sensor	Notes
3242-2	Diesel Particulate Filter Intake Gas Temperature (bank 1) : Erratic, Intermittent, or Incorrect	20	There are several connectors between the Engine Control Module (ECM) and the sensor. The connectors are 6-pin connectors. One 6-pin connector (19) is on the sensor group for the Diesel Particulate Filter (DPF). One 6-pin connector (8) is near the ECM.	The ECM compares the signals from the three sensors for a Diesel Particulate Filter (DPF) whenever the following conditions are met: The keyswitch is turned to the ON position. 15 seconds elapse. There are no -3 codes or -4 codes for any of the sensors. The engine is started. The ECM verifies that the signal from each sensor is on the appropriate terminal of the P2 connector. The ECM activates a -2 code if a signal is detected on the wrong terminal or if the signal is incorrect. The following conditions can cause a -2 code: The sensor group for the DPF is electrically connected to the wiring. However, the sensor group is not mechanically connected to the DPF. There is a loose clamp in the exhaust piping between the outlet of the Aftertreatment Regeneration Device (ARD) and the inlet to the DPF. The tubes between the DPF and the sensor group are obstructed. The obstruction can be caused by soot or frozen condensation. There is a problem with the wiring between the sensor group and the ECM. Usually, the wiring problem is in the vehicle wiring harness.
3246-2	Diesel Particulate Filter Outlet Gas Temperature (bank 1) : Erratic, Intermittent, or Incorrect
3251-2	Diesel Particulate Filter Differential Pressure (bank 1) : Erratic, Intermittent, or Incorrect
3276-2	Diesel Particulate Filter Intake Gas Temperature (bank 2) : Erratic, Intermittent, or Incorrect
3280-2	Diesel Particulate Filter Outlet Gas Temperature (bank 2) : Erratic, Intermittent, or Incorrect
3285-2	Diesel Particulate Filter Differential Pressure (bank 2) : Erratic, Intermittent, or Incorrect
Follow the troubleshooting procedure in order to identify the root cause of the problem.

Show/hide table

Table 2
-3 Diagnostic Trouble Codes for Active Analog Sensors
J1939 Code	Description	Callout in the Illustrations for Component Location	Location of the Connector for the Sensor	Notes
94-3	Engine Fuel Delivery Pressure : Voltage Above Normal	2	Sensor	The ECM monitors the signal voltage from the sensor in order to detect a problem in the circuit. When the ECM detects signal voltage that is above a threshold, the ECM activates a -3 diagnostic code. The high voltage condition must exist for a period in order for the diagnostic code to be activated. During this test procedure, wait for 30 seconds after you create the test condition. Then, check for the code. The most likely cause of a -3 code is a problem in an electrical connector or wiring. The following conditions can cause a -3 code: Electrical connectors that are not fully connected A socket is fretted. The pin does not contact the socket because the socket has become loose. Electrical wiring is broken. The wire insulation appears to be okay. However, the electrical conductor inside the insulation is broken. This type of failure usually occurs when vibration causes the wire to bend back and forth. This type of failure usually occurs near an electrical connector.
100-3	Engine Oil Pressure : Voltage Above Normal	9	Sensor
101-3	Engine Crankcase Pressure : Voltage Above Normal	10	Sensor
102-3	Engine Intake Manifold #1 Pressure : Voltage Above Normal	1	Sensor
2948-3	Engine Intake Valve Actuation System Oil Pressure : Voltage Above Normal	11	Sensor
3241-3	Exhaust Gas Temperature 1 : Voltage Above Normal	17	7
3242-3	Diesel Particulate Filter Intake Gas Temperature (bank 1) : Voltage Above Normal	20	19 and 8
3245-3	Exhaust Gas Temperature 3 : Voltage Above Normal	15	7
3246-3	Diesel Particulate Filter Outlet Gas Temperature (bank 1) : Voltage Above Normal	20	19 and 8
3249-3	Exhaust Gas Temperature 2 : Voltage Above Normal	16	7
Follow the troubleshooting procedure in order to identify the root cause of the problem.

Show/hide table

Table 3
-3 Diagnostic Trouble Codes for Active Analog Sensors
J1939 Code	Description	Callout in the Illustrations for Component Location	Location of the Connector for the Sensor	Notes
3251-3	Diesel Particulate Filter Differential Pressure (bank 1) : Voltage Above Normal	20	19 and 8	The ECM monitors the signal voltage from the sensor in order to detect a problem in the circuit. When the ECM detects signal voltage that is above a threshold, the ECM activates a -3 diagnostic code. The high voltage condition must exist for a period in order for the diagnostic code to be activated. During this test procedure, wait for 30 seconds after you create the test condition. Then, check for the code. The most likely cause of a -3 code is a problem in an electrical connector or wiring. The following conditions can cause a -3 code: Electrical connectors that are not fully connected A socket is fretted. The pin does not contact the socket because the socket has become loose. Electrical wiring is broken. The wire insulation appears to be okay. However, the electrical conductor inside the insulation is broken. This type of failure usually occurs when vibration causes the wire to bend back and forth. This type of failure usually occurs near an electrical connector.
3276-3	Diesel Particulate Filter Intake Gas Temperature (bank 2) : Voltage Above Normal	20	19 and 8
3280-3	Diesel Particulate Filter Outlet Gas Temperature (bank 2) : Voltage Above Normal	20	19 and 8
3285-3	Diesel Particulate Filter Differential Pressure (bank 2) : Voltage Above Normal	20	19 and 8
3480-3	Aftertreatment #1 Fuel Pressure #1 : Voltage Above Normal This diagnostic code relates to main fuel pressure.	5	Sensor
4077-3	Aftertreatment #1 Fuel Pressure #2 : Voltage Above Normal This diagnostic code relates to pilot fuel pressure.	5	Sensor
3830-3	Aftertreatment 1 Secondary Air Differential Pressure : Voltage Above Normal	13	Sensor
520193-3	CGI Gas Temperature : Voltage Above Normal	14	12
520196-3	CGI Differential Pressure : Voltage Above Normal	4	Sensor
520197-3	CGI Absolute Pressure : Voltage Above Normal	3	Sensor
Follow the troubleshooting procedure in order to identify the root cause of the problem.

Show/hide table

Table 4
-4 Diagnostic Trouble Codes for Active Analog Sensors
J1939 Code	Description	Callout in the Illustrations for Component Location	Location of the Connector for the Sensor	Notes
94-4	Engine Fuel Delivery Pressure : Voltage Below Normal	2	Sensor	The ECM monitors the signal voltage from the sensor in order to detect a problem in the circuit. When the ECM detects signal voltage that is below a threshold, the ECM activates a -4 diagnostic code. The low voltage condition must exist for a period in order for the diagnostic code to be set. During this test procedure, wait for 30 seconds after you create the test condition. Then, check for the code. The most likely cause of a -4 code is a problem in an electrical connector or wiring. The following conditions can cause these codes: Moisture in a connector can cause a low signal voltage. Melted insulation allows the conductors to create a short circuit. Wire insulation that is worn allows the conductors to create a short circuit. The insulation is worn from the wire when the wire rubs against a component.
100-4	Engine Oil Pressure : Voltage Below Normal	9	Sensor
101-4	Engine Crankcase Pressure : Voltage Below Normal	10	Sensor
102-4	Engine Intake Manifold #1 Pressure : Voltage Below Normal	1	Sensor
2948-4	Engine Intake Valve Actuation System Oil Pressure : Voltage Below Normal	11	Sensor
3241-4	Exhaust Gas Temperature 1 : Voltage Below Normal	17	7
3242-4	Diesel Particulate Filter Intake Gas Temperature (bank 1) : Voltage Below Normal	20	19 and 8
3245-4	Exhaust Gas Temperature 3 : Voltage Below Normal	15	7
3246-4	Diesel Particulate Filter Outlet Gas Temperature (bank 1) : Voltage Below Normal	20	19 and 8
3249-4	Exhaust Gas Temperature 2 : Voltage Below Normal	16	7
Follow the troubleshooting procedure in order to identify the root cause of the problem.

Show/hide table

Table 5
-4 Diagnostic Trouble Codes for Active Analog Sensors
J1939 Code	Description	Callout in the Illustrations for Component Location	Location of the Connector for the Sensor	Notes
3251-4	Diesel Particulate Filter Differential Pressure (bank 1) : Voltage Below Normal	20	19 and 8	The ECM monitors the signal voltage from the sensor in order to detect a problem in the circuit. When the ECM detects signal voltage that is below a threshold, the ECM activates a -4 diagnostic code. The low voltage condition must exist for time in order for the diagnostic code to be set. During this test procedure, wait for 30 seconds after you create the test condition. Then, check for the code. The most likely cause of a -4 code is a problem in an electrical connector or wiring. The following conditions can cause these codes: Moisture in a connector can cause a low signal voltage. Melted insulation allows the conductors to create a short circuit. Wire insulation that is worn allows the conductors to create a short circuit. The insulation is worn from the wire when the wire rubs against a component.
3276-4	Diesel Particulate Filter Intake Gas Temperature (bank 2) : Voltage Below Normal	20	19 and 8
3280-4	Diesel Particulate Filter Outlet Gas Temperature (bank 2) : Voltage Below Normal	20	19 and 8
3285-4	Diesel Particulate Filter Differential Pressure (bank 2) : Voltage Below Normal	20	19 and 8
3480-4	Aftertreatment #1 Fuel Pressure #1 : Voltage Below Normal This diagnostic code relates to main fuel pressure.	5	Sensor
4077-4	Aftertreatment #1 Fuel Pressure #2 : Voltage Below Normal This diagnostic code relates to pilot fuel pressure.	5	Sensor
3830-4	Aftertreatment 1 Secondary Air Differential Pressure : Voltage Below Normal	13	Sensor
520193-4	CGI Gas Temperature : Voltage Below Normal	14	12
520196-4	CGI Differential Pressure : Voltage Below Normal	4	Sensor
520197-4	CGI Absolute Pressure : Voltage Below Normal	3	Sensor
Follow the troubleshooting procedure in order to identify the root cause of the problem.

Show/hide table

Table 6
-20 and -21 Diagnostic Trouble Codes for Active Analog Sensors
J1939 Code	Description	Callout in the Illustrations for Component Location	Location of the Connector for the Sensor	Notes
3241-20	Exhaust Gas Temperature 1 : Data Drifted High	17	7	These codes indicate that the temperature at the sensor briefly exceeded 1200 °C (2200 °F). Clear the code. No troubleshooting is required.
3245-20	Exhaust Gas Temperature 3 : Data Drifted High	17	7
3249-20	Exhaust Gas Temperature 2 : Data Drifted High	17	7
520193-20	CGI Gas Temperature : Data Drifted High	14	12
3251-20	Diesel Particulate Filter Differential Pressure (bank 1) : Data Drifted High	18	N/A	The engine speed is zero rpm. There is no differential pressure across the DPF. The signal from the differential pressure sensor for the DPF is above 0.95 VDC or below 0.65 VDC. The signal is not in the diagnostic band. The code is latched. The code cannot be cleared with the Caterpillar Electronic Technician (ET). Troubleshoot the code in order to clear the code. The following conditions can cause these codes: There is moisture inside an electrical connector. This condition causes the signal voltage to shift slightly. There is an obstruction in the tubing between the DPF and the sensor group for the DPF. The differential pressure sensor interprets the obstruction as differential pressure. The sensor output voltage shifts in response to the differential pressure. The sensor group has failed.
3285-20	Diesel Particulate Filter Differential Pressure (bank 2) : Data Drifted High	18	N/A
3251-21	Diesel Particulate Filter Differential Pressure (bank 1) : Data Drifted Low	18	N/A
3285-21	Diesel Particulate Filter Differential Pressure (bank 2) : Data Drifted Low	18	N/A
Follow the troubleshooting procedure in order to identify the root cause of the problem.

Locations of the Sensors and the Sensor Connectors on C13 Engines

Show/hide table




Illustration 1	g01422564
Left side of a C13 engine Sensors (16) and (17) share a 4-pin connector at location (7). The color of the inside of this harness connector is red. The connector for sensor (15) is a 4-pin connector at location (7). The color of the inside of this harness connector is gray. (1) Intake manifold pressure sensor (2) Fuel pressure sensor (if equipped) (3) Absolute pressure sensor for the clean gas induction system (4) Differential pressure sensor for the clean gas induction system (5) This fuel pressure sensor for pilot fuel relates to Aftertreatment Fuel Pressure #2. (6) This fuel pressure sensor for main fuel relates to Aftertreatment Fuel Pressure #1. (7) Sensor connectors for sensors (15), (16), and (17) (8) 6-pin connectors for the sensor group for the DPF (9) Oil pressure sensor (10) Crankcase pressure sensor

Show/hide table




Illustration 2	g01422565
Right side of a C13 engine Sensors (16) and (17) share a 4-pin connector at location (7). The color of the inside of this harness connector is red. The connector for sensor (15) is a 4-pin connector at location (7). The color of the inside of this harness connector is gray. The sensor connector for sensor (14) is a 4-pin connector at location (12). Only three of the pins are used. (11) The intake valve actuation pressure sensor is located underneath the valve cover. (12) Sensor connector for sensor (14) (13) Differential pressure sensor for the combustion air supply (14) Temperature sensor for the clean gas induction system (15) Flame boundary temperature sensor (16) Flame detection temperature sensor (17) Turbocharger outlet temperature sensor

Locations of the Sensors and the Sensor Connectors on C15 Engines

Show/hide table




Illustration 3	g01422567
Left side of a C15 engine Sensors (16) and (17) share a 4-pin connector at location (7). The color of the inside of this harness connector is red. The connector for sensor (15) is a 4-pin connector at location (7). The color of the inside of this harness connector is gray. (1) Intake manifold pressure sensor (2) Fuel pressure sensor (if equipped) (3) Absolute pressure sensor for the clean gas induction system (4) Differential pressure sensor for the clean gas induction system (5) This fuel pressure sensor for pilot fuel relates to Aftertreatment Fuel Pressure #2. (6) This fuel pressure sensor for main fuel relates to Aftertreatment Fuel Pressure #1. (7) Sensor connectors for sensors (15), (16), and (17) (8) 6-pin connectors for the sensor group for the DPF (9) Oil pressure sensor (10) Crankcase pressure sensor

Show/hide table




Illustration 4	g01422568
Right side of a C15 engine Sensors (16) and (17) share a 4-pin connector at location (7). The color of the inside of this harness connector is red. The connector for sensor (15) is a 4-pin connector at location (7). The color of the inside of this harness connector is gray. The connector for sensor (14) is a 4-pin connector at location (12). Only three of the pins are used. (11) Intake valve actuation pressure sensor (12) Connector for sensor (14) (13) Differential pressure sensor for the combustion air supply (14) Temperature sensor for the clean gas induction system (15) Flame boundary temperature sensor (16) Flame detection temperature sensor (17) Turbocharger outlet temperature sensor

Location of the Sensor Group and Connector on a Typical DPF

Show/hide table




Illustration 5	g01422569
Typical diesel particulate filters (18) Tubing (19) Connector for the sensor group (20) Sensor group

Diagnostics on Cat ET

Wiggle Test - The wiggle test allows you to monitor the status of the signals from the sensors while you wiggle the wiring. The test helps to identify faulty electrical connections.

For additional information regarding the wiggle test, refer to the documentation that accompanies your Cat ET software.

Show/hide table




Illustration 6	g02374136
Schematic for the active sensors

Show/hide table




Illustration 7	g01754336
Schematic for the sensors on the DPF

Test Step 1. Determine if the Code is Logged or Active

Identify the diagnostic code.

Results:

Logged -3 code or -4 code. -
Repair: Do not troubleshoot a logged code unless the code relates to an engine symptom. If the code is logged and the code does not relate to an engine symptom, clear the code.

If the code is logged and the code relates to an engine symptom, proceed to Test Step 2.
Logged or active -2 code - Proceed to Test Step 7.
Active -3 code or -4 code. - Proceed to Test Step 3.
Logged -20 code for a thermocouple. - The temperature at the sensor briefly exceeded 1200 °C (2200 °F).
Repair: Clear the code. No troubleshooting is required.

STOP
Active or logged -20 code or -21 code. - Proceed to Test Step 8.

Test Step 2. Perform the Wiggle Test

Carefully following this procedure is the best way to identify the root cause of an intermittent problem.

Verify that the engine is OFF and that the keyswitch is ON.
Configure Cat ET for the wiggle test. Select the status group that includes the parameter that relates to the code. Start the wiggle test.
Slowly wiggle the wiring and the connectors between the P2 connector and the sensor. Pay particular attention to the wiring near each connector. Be sure to wiggle all of the wiring between the P2 connector and the sensor.
As you wiggle the wiring, observe the wiring and the connectors. Look for these problems:
- Loose connectors or damaged connectors
- Moisture on the connectors or the wiring
- Damage that is caused by excessive heat
- Damage that is caused by chafing
- Improper routing of wiring
- Damaged insulation

Expected Result:

The wiring failed the wiggle test.

Results:

The wiring failed the wiggle test. -
Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.

STOP
The wiring passed the wiggle test. -
Repair: There may be a problem inside a connector. Perform the following procedure:
1. Disconnect the connectors for the sensor. Carefully inspect the terminals in each connector for proper installation. Each terminal must be clean and dry. Clean the terminals, if necessary.
2. Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems.
  Note: Numerous diagnostic codes will become active when you disconnect the J2/P2 connectors. Ignore the additional codes and clear the codes when you are finished.
3. Disconnect the J2/P2 connectors.
4. Identify the P2 socket that relates to the diagnostic code. Carefully inspect the socket for proper installation. The socket must be clean and dry. Clean the socket, if necessary.
5. Insert a pin into the socket. Verify that the socket grips the pin firmly. Repair any problems.
6. Connect all connectors.
7. Activate the wiggle test. Verify that the wiring passes the wiggle test.
  Note: If the code is only activated during a regeneration, start the engine and allow the engine to warm until a regeneration can be forced.
  If the diagnostic code does not recur, return the engine to service.
If the diagnostic code recurs, proceed to Test Step 3.

Test Step 3. Check the Supply Voltage at the Sensor Connector

Measure the voltage between terminal 1 (+5 V supply) and terminal 2 (Return) at the harness connector for the sensor that relates to the code.

Expected Result:

The voltage is between 4.5 VDC and 5.5 VDC.

Results:

OK - The voltage is between 4.5 VDC and 5.5 VDC. The supply voltage is at the sensor connector. Record the voltage measurement. If you are troubleshooting a -3 diagnostic code, proceed to Test Step 4. If you are troubleshooting a -4 diagnostic code, proceed to Test Step 6.
Not OK - The voltage is less than 4.5 VDC or the voltage is greater than 5.5 VDC.
Repair: The voltage of the sensor supply is incorrect. Refer to Troubleshooting, "Sensor Supply - Test".

STOP

Test Step 4. Check for Battery Voltage on the Signal Wire

Measure the voltage between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code.

Expected Result:

The voltage measurement is less than the +Battery voltage.

Results:

Yes - The voltage measurement is less than the +Battery voltage. The signal wire is not shorted to the +Battery. Proceed to Test Step 5.
No - The voltage measurement is approximately +Battery voltage. The signal wire is shorted to the +Battery.
Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.

STOP

Test Step 5. Check the Signal Wire for an Open Circuit

Disconnect the sensor that relates to the diagnostic code.
Connect a jumper wire between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code. The wire will replace the sensor with a short circuit.
Look for a -4 diagnostic code.

Expected Result:

The -3 code does not change to a -4 code when the jumper wire is connected.

Results:

Yes - The -3 code does not change to a -4 code when the jumper wire is connected.
Repair: There is a problem with the wiring between the sensor and the P2 connector. The most probable cause of a wiring problem is a problem with a connector. Perform the following procedure:
1. Carefully inspect the wiring at the connector for the sensor. Pull on the wire in order to verify that the wire is crimped to the terminal. Pulling verifies that the terminal is properly installed in the connector.
2. Carefully inspect the wiring at the P2 connector. Pull on the wire in order to verify that the wire is crimped to the terminal. Pulling verifies that the terminal is properly installed in the connector.
3. Disconnect the connectors in order to verify that the wiring and terminals are installed correctly. Make the necessary repairs.
STOP
No - The -3 code changes to a -4 code when the jumper wire is connected. The wiring harness is OK.
Repair: Perform the following procedure:
1. Remove the jumper wire.
2. Connect a new sensor to the engine harness. Do not install the sensor into the engine.
3. Verify that the active -3 diagnostic code does not recur.
4. Install the sensor into the engine.
5. Clear all logged diagnostic codes and return the engine to service.
STOP

Test Step 6. Disconnect the Sensor and Check for a -3 Diagnostic Code

Disconnect the sensor that applies to the -4 diagnostic code.
Look for a -3 diagnostic code.
Connect the sensor and look for a -4 diagnostic code.

Expected Result:

When the sensor is disconnected, the -4 code remains.

Results:

Yes - When the sensor is disconnected, the -4 code remains.
Repair: There is a problem with the wiring between the sensor and the P2 connector. The most probable cause of a wiring problem is a problem with a connector. Perform the following procedure:
1. Carefully inspect the wiring at the connector for the sensor. Pull on the wire in order to verify that the wire is crimped to the terminal. Pulling verifies that the terminal is properly installed in the connector.
2. Carefully inspect the wiring at the P2 connector. Pull on the wire in order to verify that the wire is crimped to the terminal. Pulling verifies that the terminal is properly installed in the connector.
3. Disconnect the connectors in order to verify that the wiring and terminals are installed correctly. Make the necessary repairs.
STOP
No - When the sensor is disconnected, the -4 code changes to a -3 code. There is a problem with the sensor.
Repair: Perform the following procedure:
1. Connect a new sensor to the engine harness. Do not install the sensor into the engine.
2. Verify that the active -4 diagnostic code does not recur.
3. Install the sensor into the engine.
4. Clear all logged diagnostic codes and return the engine to service.
STOP

Test Step 7. Check the Wiring and the Sensor Group for the DPF

Show/hide table




Illustration 8	g01426519
Typical DPF (21) Thermocouple (18) Tube

Verify that both thermocouples (21) are threaded into the DPF.
Remove both tubes (18) and check the tubes for obstructions.
Install the tubes. Verify that all four nuts for the tubes are tight.
Inspect the exhaust piping between the ARD and the inlet to the DPF. Verify that the exhaust piping is free of holes and of cracks and that all clamps are securely fastened.
Clear the -2 code.
Turn the keyswitch to the OFF position.
Turn the keyswitch to the ON position. Wait for 15 seconds.
Start the engine.
Check for a recurrence of the -2 code.

Expected Result:

The -2 code does not return.

Results:

Yes - The -2 code does not return. The -2 code was caused by a mechanical problem.
STOP

No - The -2 code returns. There is not a mechanical problem. There is a wiring problem.

Repair: Perform the following procedure:

Refer to Illustration 9. Disconnect the harness connector from the sensor group.
Note: The ECM will activate a -3 code for all three sensors.
Show/hide table

Illustration 9 g01754913

Harness connector for the DPF
(3) Differential pressure
(2) Return
(4) Inlet temperature
(5) Outlet temperature

Connect a jumper wire between the terminals that are listed in Table 7. Wait for a -4 code to become active.

Show/hide table

Table 7
Code That Applies to Each Terminal on the Harness Connector for the DPF
Terminals for the Jumper Wire		Code That Should Be Activated
Jumper wire between terminal 2 (return) and terminal 3 (differential pressure)		-4 Code for Differential Pressure
Jumper wire between terminal 2 (return) and terminal 4 (inlet temperature)		-4 Code for Inlet Temperature
Jumper wire between terminal 2 (return) and terminal 5 (outlet temperature)		-4 Code for Outlet Temperature

If a wrong code is activated, the wiring is incorrect. Refer to Illustration 7. Identify the problem with the wiring. Make the necessary repairs.
If the correct code is activated for all three signal terminals, the wiring is OK. There is a wiring problem inside the sensor group. Replace the sensor group.
Perform the following procedure in order to verify that your repair has solved the problem. Clear the codes for the sensor group.
1. Turn the keyswitch to the OFF position.
2. Turn the keyswitch to the ON position. Wait for 15 seconds.
3. Start the engine. Verify that there are no -2 codes for the sensors for DPF.

STOP

Test Step 8. Troubleshoot the Incorrect Signal

If the vehicle has a single DPF, disconnect the harness connector from the sensor group. if the vehicle has two filters, perform the following procedure in order to determine the appropriate DPF:
1. Gain access to a harness connector for either sensor group. Disconnect the harness connector from the sensor group. Use the information in Illustration 10 in order to determine the appropriate DPF for the diagnostic code.
2. Disconnect the appropriate harness connector.
Clean the harness connector and the electrical connector on the sensor group. Both of the connectors must be clean and dry.
Connect the electrical connectors.
Turn the keyswitch to the OFF position. Wait for five seconds. Turn the keyswitch to the ON position. Wait for ten seconds.

Expected Result:

The -20 code or the -21 code clears automatically .

Results:

The -20 code automatically clears. - Moisture or debris was causing the signal voltage to be incorrect. The problem is resolved.
STOP
The -20 code or the -21 code remains. - Additional troubleshooting is required.
Repair: Perform the following procedure.
1. Remove the tubing from the appropriate DPF.
2. Check the tubing for moisture and for obstructions. The tubing must be dry and free of obstructions. Remove any moisture and obstructions from the tubing.
3. Install the tubing. Verify that every connection is tight.
4. Turn the keyswitch to the OFF position. Wait for five seconds. Turn the keyswitch to the ON position. Wait for ten seconds.
  If the -20 code or the -21 code automatically clears, the problem is resolved. The obstructed tubing was causing the signal voltage to be incorrect. The problem is resolved.
  If the -20 code or the -21 code remains, there is a problem with the sensor group. Replace the sensor group.
STOP