C7 and C9 Industrial Engines Caterpillar

Sensor Signal (Analog, Active) - Test

Usage:

C7 JRA

Use this procedure to troubleshoot any suspect problems with the following sensors:

Injection actuation pressure sensor
Boost pressure sensor
Atmospheric pressure sensor
Fuel pressure sensor
Engine oil pressure sensor
Auxiliary pressure sensor (if equipped)

This procedure covers the following diagnostic codes:

094-03 Fuel Pressure open/short to +batt
094-04 Fuel Pressure short to ground
100-03 Engine Oil Pressure open/short to +batt
100-04 Engine Oil Pressure short to ground
102-03 Boost Pressure Sensor short to +batt
102-04 Boost Pressure Sensor short to ground
274-03 Atmospheric Pressure open/short to +batt
274-04 Atmospheric Pressure short to ground

The troubleshooting procedures for the diagnostic codes of each pressure sensor are identical. The Engine Control Module (ECM) sends a 5 V supply to terminal A of each sensor. The sensor common connection is connected to terminal B of each sensor. The signal voltage from terminal C of each sensor is sent to the appropriate ECM connector.

Pull-up Voltage

The ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage in order to detect an open in the signal circuit. When the ECM detects the presence of a voltage that is above a threshold on the signal wire, the ECM will generate a -03 diagnostic code.

If the sensor is disconnected at the sensor connector, the presence of pull-up voltage at the sensor connector indicates that the signal wire and the return wire from the sensor connector to the ECM are good.

If the sensor is disconnected at the sensor connector, the absence of pull-up voltage at the sensor connector indicates an open in the signal wire, an open in the return wire, or a short to ground.

If the sensor is disconnected at the sensor connector and the voltage on the signal wire at the sensor connector is different from pull-up voltage, the signal wire is shorted to another wire in the harness.

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Illustration 1	g01119880
Schematic for the engine pressure sensors

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Illustration 2	g01121143
Left side view (1) Boost pressure sensor (2) Atmospheric pressure sensor (3) J2/P2 connectors (4) J1/P1 connectors (5) Engine oil pressure sensor

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Illustration 3	g01121144
The location of the fuel pressure sensor depends on the engine configuration. (6) Fuel pressure sensor

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Illustration 4	g01123383
P2 terminals that are associated with the engine pressure sensors (P2-15) Boost pressure (P2-17) Return (P2-28) Engine oil pressure (P2-40) Fuel pressure (P2-54) Return (P2-57) Atmospheric pressure (P2-72) +5 VDC (P2-80) +5 VDC (P2-85) Injection actuation pressure

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Illustration 5	g01123384
P1 terminals that are associated with the engine pressure sensors (P1-2) +5 VDC (P1-3) Return (P1-15) Auxiliary pressure

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Illustration 6	g01123211
Connectors for the sensors (A) Supply (B) Return (C) Signal

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Illustration 7	g01120120
J61 and P61 terminals that are associated with the engine pressure sensors (14) +5 VDC (15) Return (33) Auxiliary pressure

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Table 1
Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and Wiring A. Turn the keyswitch to the OFF position. B. Thoroughly inspect connectors (3) and (4). Thoroughly inspect the connectors for each engine pressure sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect". C. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the engine pressure sensors. D. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect". E. Check the harness and wiring for abrasions and for pinch points from each sensor back to the ECM.	Electrical Connectors and Wiring	Results: The harness and wiring are OK. Proceed to Test Step 2. Results: There is a problem in the wiring and/or the connectors. Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the problem is resolved. STOP
2. Check the Voltage on the +5 V Supply Wire A. Turn the keyswitch to the OFF position. B. Disconnect the harness connectors for the following sensors: · Injection actuation pressure sensor J500/P500 · Boost pressure sensor J200/P200 · Atmospheric pressure sensor J203/P203 · Fuel pressure sensor J209/P209 · Engine oil pressure sensor J201/P201 · Auxiliary pressure sensor J220/P220 (if equipped) C. Turn the keyswitch to the ON position. D. Measure the voltage between terminals A (+5 VDC) and B (Return) at each sensor connector on the engine harness. E. Turn the keyswitch to the OFF position. F. Connect all of the sensors.	5.0 ± 0.2 VDC	Results: Each voltage measurement is 5.0 ± 0.2 VDC. Proceed to Test Step 3. Results: At least one voltage measurement is not 5.0 ± 0.20 VDC. Repair: Refer to Troubleshooting, "5 V Engine Pressure Sensor Supply Circuit - Test". STOP
3. Check for Codes A. Connect Cat® Electronic Technician (ET) to the service tool connector. B. Turn the keyswitch to the ON position. C. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 15 seconds so that any codes may become active. Look for an active diagnostic code for an engine pressure sensor. D. Determine if the problem is related to a -03 diagnostic code or a -04 diagnostic code.	Codes	Results: No diagnostic codes are active for the engine pressure sensors. Repair: If any of the above codes are logged and the engine is not running properly, refer to Troubleshooting, "Troubleshooting Without a Diagnostic Code". If the engine is running properly at this time, there may be an intermittent problem in a harness that is causing the codes to be logged. Refer to Troubleshooting, "Electrical Connectors - Inspect". STOP Results: An 04 diagnostic code is active. Proceed to Test Step 4. Results: An 03 diagnostic code is active. Proceed to Test Step 5.
4. Disconnect the Suspect Sensor in Order to Create an Open Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the sensor connector of the sensor with the -04 diagnostic code. C. Turn the keyswitch to the ON position. Wait at least 15 seconds for activation of the diagnostic codes. D. Access the "Active Diagnostic Code" screen on Cat ET. Check for an active 03 diagnostic code for the disconnected sensor. E. Turn the keyswitch to the OFF position.	Code	Results: A -04 diagnostic code was active before you disconnected the sensor. A -03 diagnostic code became active after the sensor was disconnected. Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes. STOP Results: A -04 diagnostic code was active before you disconnected the sensor. The -04 diagnostic code remained after the sensor was disconnected. Leave the sensor disconnected. Proceed to Test Step 8.
5. Check the Pull-up Voltage at the Sensor Connector A. Turn the keyswitch to the ON position. B. Disconnect the suspect sensor. C. Measure the voltage between terminals C (signal) and B (sensor return) at the harness connector for the sensor. D. Turn the keyswitch to the OFF position.	11 ± 2 VDC	Results: The voltage is 11 ± 2 VDC. The signal wire to the ECM from the sensor connector is OK. Repair: The open circuit is in the sensor or the wire between the sensor and the sensor connector. Temporarily connect a new sensor to the engine harness. Do not install the sensor in the engine. Verify that no diagnostic codes are active for the new sensor before you permanently install the sensor. STOP Results: The voltage is not 11 ± 2 VDC. Proceed to Test Step 6.
6. Check the Signal Wire for a Short Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the J1/P1 and J2/P2 connectors. C. Disconnect the harness connector for the suspect sensor. D. Identify the terminal for the signal wire on the ECM connector that is appropriate for the suspect sensor. Measure the resistance between the appropriate terminal and the remaining terminals on both ECM connectors. E. Measure the resistance between the appropriate terminal and the engine ground. F. Connect J1/P1 and J2/P2 connectors. Connect the connectors for the suspect sensor.	Open Circuit	Results: Each resistance measurement indicates an open circuit. Proceed to Test Step 7. Results: At least one resistance measurement does not indicate an open circuit. There is a problem in the wiring for the sensor. There may be a problem with a connector. Repair: Repair the wiring and/or the connector. Replace parts, if necessary. Verify that the problem is resolved. STOP
7. Create a Short at the Suspect Sensor Connector A. Turn the keyswitch to the OFF position. B. Install a jumper wire with Deutsch sockets on each end between terminals B (sensor return) and C (signal) on the harness connector for the suspect sensor. C. Turn the keyswitch to the ON position. Note: Monitor the "Active Diagnostic Codes" screen on the electronic service tool before installing the jumper wire and after installing the jumper wire. D. Observe the "Active Diagnostic Codes" screen on Cat ET. Wait at least 15 seconds so that any codes may become active. Look for a -04 diagnostic code. E. Remove the jumper wire. F. Turn the keyswitch to the OFF position.	Codes	Results: A -04 diagnostic code was active when the jumper wire was installed. A -03 diagnostic code became active when the jumper wire was removed. The engine harness and the ECM are OK. Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the new sensor, permanently install the new sensor. Clear any logged diagnostic codes. Verify that the problem is resolved. STOP Results: A -04 diagnostic code was active when the jumper wire was installed. The -04 code remained when the jumper wire was removed. Proceed to Test Step 8.

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Table 2
Troubleshooting Test Steps	Values	Results
8. Check the Operation of the ECM A. Turn the keyswitch to the OFF position. B. Check the operation of the ECM by creating an open at the ECM. Note: Disconnecting the return wire from the ECM will generate an open circuit diagnostic code for all sensors that are connected to the return wire. Ignore the additional codes. Troubleshoot the original diagnostic code and clear the codes when you are finished. C. Turn the keyswitch to the ON position. D. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 15 seconds so that any codes may become active. Note: An -03 diagnostic code should be active for the suspect sensor. E. Turn the keyswitch to the OFF position. F. Check the operation of the ECM by creating a short circuit at the ECM. G. Turn the keyswitch to the ON position. H. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 15 seconds so that any codes may become active. Note: A short circuit diagnostic code (04) should be active when the wire jumper is installed. I. Turn the keyswitch to the OFF position. J. Remove the jumper wire. Return the wiring to the original configuration.	03 diagnostic code	Result: The ECM is operating properly. There is a problem in the wiring between the ECM and the sensor connector. Repair: If the code is active for more than one sensor, the problem is most likely in the return wire for the sensor. The problem may be in a connector. Repair the return wire and/or the connector. Replace parts, if necessary. If the code is only active for one sensor, the problem is most likely in the signal wire for the sensor. Repair the signal wire and/or the connector. Replace parts, if necessary. Verify that the problem is resolved. STOP Results: One of the following conditions exists: The -03 diagnostic code is not active when the signal wire is disconnected. The -04 diagnostic code is not active when the wire jumper is installed. Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved. STOP