C7 and C9 On-Highway Engines Caterpillar

System Operation Description:

The following diagnostic codes are covered by this procedure:

• 729-5 (J1939) Engine Inlet Air Heater Driver #1 : Current Below Normal

• 729-6 (J1939) Engine Inlet Air Heater Driver #1 : Current Above Normal

This procedure can also be used to troubleshoot these components:

• The air inlet heater

• The air inlet heater relay

• The lamp for the air inlet heater

Background Information

The air inlet heater is used in order to improve the engines ability to start when the engine is cold.

The Engine Control Module (ECM) controls the operation of the air inlet heater and the ECM controls the operation of the lamp for the air inlet heater through the air inlet heater relay.

The operation of the air inlet heater is determined by three different cycle times:

• ECM powerup and preheat cycle

• Engine cranking

• Engine on (running)

The cycle time is determined by the following items:

• Engine parameters

• Vehicle speed

• Service brake

Effects of Vehicle Speed on the Operation of the Air Inlet Heater and on the Operation of the Brake Pedal Position.

The air inlet heater is turned off when the brake pedal is depressed and the vehicle speed is equal to 8 km/h (5 mph) or greater than 8 km/h (5 mph).

If a diagnostic code for the vehicle speed sensor is active, the ECM will assume that the vehicle speed is above 8 km/h (5 mph). If an active diagnostic code is triggered for the vehicle speed sensor, the ECM will disable the heater when the brakes are applied.

The ECM Powerup and Preheat Cycle.

The temperatures that are indicated below are not conversions. These temperatures are representations of the sum of two variables. The following procedure explains the process for calculating the temperatures that are shown in °F:

• Convert the reading for the coolant temperature from °C to °F.

• Convert the reading for the intake manifold air temperature from °C to °F.

• Add the two conversions together in order to arrive at the correct conversion for the sum in °F.

The lamp for the air inlet heater should turn on for a minimum of 2 seconds when the ECM is first powered up. The lamp should turn on regardless of the coolant temperature.

For altitudes below 1678 m (5500 ft), the ECM will signal the air inlet heater to stay on for 30 seconds if the sum of the coolant temperature and the intake manifold air temperature is less than 40 °C (104 °F). For altitudes above 1678 m (5500 ft), the ECM will signal the air inlet heater to stay on for 30 seconds if the sum of the coolant temperature and the intake manifold air temperature is less than 53 °C (127 °F).

The air inlet heater and the lamp for the air inlet heater should turn on. The air inlet heater and the lamp for the air inlet heater should turn off when the cycle is complete.

The ECM will control the air inlet heater during engine cranking if the operator starts the engine before the end of the heating cycle.

Engine Cranking

If the conditions that are stated below are satisfied, during engine cranking the air inlet heater will turn on. The heater will remain on while the engine is cranking. The air inlet heater will reactivate for 30 seconds if the engine fails to start.

For altitudes below 1678 m (5500 ft), the ECM will signal the air inlet heater to stay on for 30 seconds if the sum of the coolant temperature and the intake manifold air temperature is less than 40 °C (104 °F). For altitudes above 1678 m (5500 ft), the ECM will signal the air inlet heater to stay on for 30 seconds if the sum of the coolant temperature and the intake manifold air temperature is less than 53 °C (127 °F).

Engine On (Running)

The operation of the air inlet heater is determined by the coolant temperature and the intake manifold air temperature after the engine has started. If the combined temperature is less than 40 °C (104 °F), the engine start cycle begins. The engine start cycle has two segments:

• Continuous mode

• On/off cycling mode

The continuous mode lasts for a maximum of 7 minutes. The on/off cycling mode can last for a maximum of 13 minutes. The air inlet heater is turned on and the air inlet heater is turned off for 10 seconds during the on/off cycling mode. The air inlet heater will turn off when the sum of the coolant temperature and the intake manifold air temperature exceeds 63 °C (145 °F) under an altitude below 1678 m (5500 ft). For altitudes above 1678 m (5500 ft), the ECM will signal the air inlet heater to turn off if the sum of the coolant temperature and the intake manifold air temperature is less than 53 °C (127 °F).

Active Open Circuit or Short Circuit Diagnostic Codes

The air inlet heater will turn on if the coolant temperature sensor has an active open circuit diagnostic code or an active short circuit diagnostic code and the intake manifold air temperature is less than 10 °C (50 °F).

The air inlet heater will turn on if the intake manifold air temperature sensor has an active open circuit diagnostic code or an active short circuit diagnostic code and the coolant temperature is less than 40 °C (104 °F).

Note: The coolant temperature and the intake manifold temperature are measured in degree Celsius. Caterpillar Electronic Technician (ET) can display the coolant temperature and the intake manifold temperature in °C or in °F. The ECM adds the coolant temperature and the intake manifold temperature together. Then, the ECM uses the sum of the coolant temperature and the intake manifold air temperature in order to determine if the air inlet heater should be on or off. Illustration 3 is a visual aid for troubleshooting the operation of the air inlet heater. The temperatures in °F are not a direct conversion of the temperatures in °C.

Illustration 1	g02798362
Schematic of the air inlet heater

Illustration 2	g01172732
(P2-5) Air inlet heater relay

Illustration 3	g01380188
Operational chart for the air inlet heater

Test Step 1. Inspect the Electrical Connectors And the Wiring

1. Thoroughly inspect the J501/P501 air inlet heater relay connector and inspect the J2/P2 ECM connector. Inspect the J648/P648 air inlet heater lamp connector and inspect the terminal connections on the air inlet heater relay. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the air inlet heater.

3. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

4. Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM.

Expected Result:

All connectors, pins, and sockets are coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The electrical connectors and the wiring are OK. Proceed to Test Step 2.

• Not OK - There is a problem with the electrical connectors or the wiring.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Use the "Intake Air Heater Enable Test" to Check the Circuit

1. Turn the keyswitch to the ON position.

   The lamp for the air inlet heater should illuminate for 2 seconds. The lamp for the air inlet heater should shut off.

2. Establish communication between Cat ET and the engine ECM. Refer to Troubleshooting, "Electronic Service Tools", if necessary.

3. Go to the "Intake Air Heater Enable Test".

4. Start the test and listen for a click from the air inlet heater relay.

   Note: The air inlet heater relay is located on the front left side of the engine.

   Note: Do not leave the "Intake Air Heater Enable Test" on. Avoid unnecessary cycling of the air inlet heater in order to prevent the battery from discharging. The "Intake Air Heater Enable Test" has a 1 minute timer. When the 1 minute time expires, the test will stop.

Expected Result:

Result 1 The lamp illuminates and the relay activates.

Result 2 The lamp illuminates and the relay activates. The air inlet heater is still suspect.

Result 3 The lamp illuminates but the relay does not activate.

Result 4 The lamp does not illuminate.

Results:

• RESULT 1 - The lamp and the relay are functioning normally.STOP

• RESULT 2 - Proceed to Test Step 3.

• RESULT 3 - There is a problem with the relay circuit. Proceed to Test Step 4.

• RESULT 4 - Proceed to Test Step 5.

Test Step 3. Check the Voltage at the Relay Contacts for the Air Inlet Heater

1. Turn the keyswitch to the OFF position.

2. Disconnect the wire from the relay terminal of the air inlet heater to the air inlet heater relay.

3. Fabricate two jumper wires with Deutsch sockets on one end and Deutsch pins on the other end. Strip a small amount of insulation from the middle of one jumper wire.

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Illustration 4	g01121595
Connections for the test lamp

4. Disconnect J501/P501 and insert the jumper wires in the electrical connectors.

5. Connect a voltage test lamp from the disconnected relay terminal to the jumper wire that is connected to J501 and P501 terminals.

6. Turn the keyswitch to the ON position.

7. Go to the "Intake Air Heater Enable Test" on Cat ET.

8. Start the test and watch the voltage test lamp.

   Note: Do not leave the "Intake Air Heater Enable Test" on. Avoid unnecessary cycling of the air inlet heater in order to prevent the battery from discharging. The "Intake Air Heater Enable Test" has a 1 minute timer. When the 1 minute time expires, the test will stop.

Expected Result:

The test lamp turned on and the test lamp turned off with the "Intake Air Heater Enable Test".

Results:

• OK - The test lamps indications are correct. The air inlet heater relay and the +Battery connection to the air inlet heater relay are OK. Leave the wire disconnected from the relay terminal. Proceed to Test Step 6.

• Not OK - The test lamps indications are incorrect. The test lamp does not illuminate or the test lamp remains on after the test lamp illuminates. Connect the wire to the relay terminal. Proceed to Test Step 7.

Test Step 4. Check the Voltage at the P501 Air Inlet Heater Relay Connector

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Illustration 5	g01121615
Typical example of the locations for the components (1) P648/J648 Air inlet heater lamp connector (2) J501/P501 Air inlet heater relay connector (3) Contact side to the air inlet heater (4) Contact side to the circuit protection (5) Air inlet heater relay (6) Test lamp (7) Air inlet heater relay connector (socket terminals)

1. Disconnect the J501/P501 air inlet heater relay connector.

2. Ensure that J648/P648 air inlet heater lamp connector is still connected.

3. Connect a voltage test lamp to the two terminals of the engine harness side for the P501 air inlet heater relay connector.

4. Turn the keyswitch to the ON position.

5. Go to the "Intake Air Heater Enable Test" on Cat ET.

6. Start the test and watch the voltage test lamp.

   Note: Do not leave the "Intake Air Heater Enable Test" on. Avoid unnecessary cycling of the air inlet heater in order to prevent the battery from discharging. The "Intake Air Heater Enable Test" has a 1 minute timer. When the 1 minute time expires, the test will stop.

Expected Result:

The test lamp turns on and the test lamp turns off with the "Intake Air Heater Enable Test". The wiring is OK. There is a problem with the air inlet heater.

Results:

• OK - The test lamps indications are correct.

  Repair: Replace the air inlet heater. Verify that the problem is resolved.

  STOP

• Not OK - The test lamps indications are incorrect. The relays connector is not receiving the correct voltage. Proceed to Test Step 8.

Test Step 5. Check the Voltage at the Lamp for the Air Inlet Heater

1. Turn the keyswitch to the OFF position.

2. Locate the lamp in the dash for the air inlet heater. Remove the lamp from the dash.

3. Connect a voltage test lamp between the two terminals of the lamp socket.

4. Turn the keyswitch to the ON position.

5. Go to the "Intake Air Heater Enable Test" on Cat ET.

6. Start the test and watch the voltage test lamp.

   Note: Do not leave the "Intake Air Heater Enable Test" on. Avoid unnecessary cycling of the air inlet heater in order to prevent the battery from discharging. The "Intake Air Heater Enable Test" has a 1 minute timer. When the 1 minute time expires, the test will stop.

Expected Result:

The test lamp turns on and the test lamp turns off with the "Intake Air Heater Enable Test".

Results:

• OK - The test lamps indications are correct.

  Repair: Replace the lamp for the air inlet heater. Verify that the problem has been resolved.

  STOP

• Not OK - The test lamps indications are incorrect. Reinstall the lamp for the air inlet heater. Proceed to Test Step 9.

Test Step 6. Check the Wiring for the Air Inlet Heater

1. Turn the keyswitch to the OFF position.

2. Disconnect both wires from the air inlet heater.

3. Measure the resistance between the ends of the wire that connects the air inlet heater to the air inlet heater relay.

4. Measure the resistance from the engine ground stud to the other end of the wire for the air inlet heater that connects to the ground stud.

Expected Result:

The resistance is less than 20 Ohms.

Results:

• OK - The resistance is less than 20 Ohms.

  Repair: Replace the air inlet heater. Verify that the problem is resolved.

  STOP

• Not OK - The resistance is greater than 20 Ohms.

  Repair: Repair the damaged wire. Verify that the problem is resolved.

  STOP

Test Step 7. Check the Relay Contact at the +Battery Terminal Connection

1. Turn the keyswitch to the OFF position.

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Illustration 6	g01121635
Connections for the test lamp

2. Connect a voltage test lamp from the terminal for the relay contact that connects to the circuit protection for the air inlet heater (wire K995-OR).

3. Connect the other end of the voltage test lamp to the engine ground stud.

4. Turn the keyswitch to the ON position.

Expected Result:

The test lamp illuminates when the keyswitch is placed in the ON position.

Results:

• OK - The test lamp illuminates when the keyswitch is placed in the ON position.

  Repair: Repair the wiring between the lamp for the air inlet heater and the connector J648-B. Verify that the problem has been resolved.

  STOP

• Not OK - The test lamp does not illuminate when the keyswitch is placed in the ON position.

  Repair: Inspect the circuit protection for the air inlet heater. Repair the wiring. Verify that the problem has been resolved.

  STOP

Test Step 8. Check the Battery Voltage to J648 Air Inlet Heater Lamp Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the J648/P648 air inlet heater lamp connector.

3. Connect a voltage test lamp to the terminal J648-A. Refer to Illustration 5.

4. Connect a jumper wire to the ground stud. Connect the other lead of the test lamp to the jumper wire.

5. Turn the keyswitch to the ON position.

Expected Result:

The voltage test lamp came on and the voltage test lamp stays on while the voltage test lamp is connected between J648-A and the ground stud.

Results:

• OK - Proceed to Test Step 10.

• Not OK -

  Repair: Repair the wiring. Verify that the problem has been resolved.

  STOP

Test Step 9. Check the Voltage at J648/P648 Air Inlet Heater Lamp Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the J648/P648 air inlet heater lamp connector.

3. Connect a voltage test lamp from J648-A to the engine ground stud.

4. Turn the keyswitch to the ON position.

Expected Result:

The test lamp illuminates and the test lamp remains illuminated.

Results:

• OK -

  Repair: Repair the wiring from J648-B to the lamp. Verify that the problem has been resolved.

  STOP

• Not OK -

  Repair: Repair the wiring from J648-A to the lamp. Verify that the problem has been resolved.

  STOP

Test Step 10. Check Battery Voltage to the P501 Air Inlet Heater Relay Connector

1. Turn the keyswitch to the OFF position.

2. Ensure that the J648/P648 air inlet heater lamp connector is connected.

3. Disconnect the J501/P501 air inlet heater relay connector.

4. Connect a voltage test lamp from the connector P501-1 for the air inlet heater relay to the engine ground stud.

5. Turn the keyswitch to the ON position.

Expected Result:

The voltage test lamp turns on and the voltage test lamp stays on when the keyswitch is in the ON position.

Results:

• OK - The voltage test lamp illuminates and the voltage test lamp remains illuminated when the keyswitch is in the ON position. Proceed to Test Step 11.

• Not OK - The test lamps indications are incorrect.

  Repair: Repair the wiring from J648-A to P501-1. Verify that the problem is resolved.

  STOP

Test Step 11. Check the ECM

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Illustration 7	g01117766
Pin location on breakout T (8) Air inlet heater relay

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector J648/P648 .

3. Disconnect the J2/P2 ECM connector. Install a breakout T to the J2 ECM connector only.

4. Connect a voltage test lamp from the J648-A terminal to the terminal 8 of the breakout T. Refer to Illustration 7.

5. Turn the keyswitch to the ON position.

6. Go to the "Intake Air Heater Enable Test" on Cat ET.

7. Start the test and watch the voltage test lamp.

   Note: Do not leave the "Intake Air Heater Enable Test" on. Avoid unnecessary cycling of the air inlet heater in order to prevent the battery from discharging. The "Intake Air Heater Enable Test" has a 1 minute timer. When the 1 minute time expires, the test will stop.

   Note: When the J2/P2 ECM connector is disconnected and the keyswitch is in the ON position open circuit diagnostic codes will be active or logged for all of the engine sensors. These codes are normal.

Expected Result:

The test lamp turned on and the test lamp turned off with the "Intake Air Heater Enable Test".

Results:

• OK - The test lamp turned on and the test lamp turned off with the "Intake Air Heater Enable Test". The ECM is operating correctly.

  Repair: Repair the wiring from P501 air inlet heater relay connector to the P2 connector. Verify that the problem has been resolved.

  STOP

• Not OK - The test lamps indications were incorrect. Proceed to Test Step 12.

Test Step 12. Test the Battery Voltage to the ECM

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Illustration 8	g01117719
Pin locations on breakout T (48) Unswitched +Battery (52) Unswitched +Battery (53) Unswitched +Battery (55) Unswitched +Battery (63) -Battery (65) -Battery (67) -Battery (69) -Battery (70) Keyswitch

1. Turn the keyswitch to the OFF position.

2. Disconnect the J1/P1 ECM connector and install a breakout T.

3. Connect a voltmeter to the breakout harness between Terminal 70 keyswitch power and Terminal 63 -Battery. Refer to Illustration 8.

4. Turn the keyswitch to the ON position and check the voltmeter.

5. Turn the keyswitch to the OFF position.

6. Connect a voltmeter to the breakout harness between Terminal 48 unswitched +Battery and Terminal 63 -Battery. Refer to Illustration 8.

7. Check the voltmeter.

8. At the breakout harness, connect a voltmeter between the Terminal 52 unswitched +Batt and Terminal 65 -Battery. Refer to Illustration 8.

9. Check the voltmeter.

10. At the breakout harness, connect a voltmeter between Terminal 53 unswitched +Batt and Terminal 67 -Batt. Refer to Illustration 8.

11. Check the voltmeter.

12. At the breakout harness, connect a voltmeter between Terminal 55 unswitched +Batt and Terminal 69 -Batt. Refer to Illustration 8.

13. Check the voltmeter.

Expected Result:

All of the voltage readings are between 11.0 VDC and 13.5 VDC.

Results:

• OK - All of the voltage readings are between 11.0 VDC and 13.5 VDC. The ECM is receiving the correct operating voltage. However, the ECM is not operating correctly.

  Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.

  STOP

• Not OK - At least one of the voltage readings is not between 11.0 VDC and 13.5 VDC.

  Repair: Repair the vehicle wiring or send the vehicle to the OEM dealer for repair. Verify that the problem has been resolved.

  STOP