P0542

P0542-INTAKE AIR HEATER CONTROL CIRCUIT 1 HIGH





For a complete wiring diagram refer to the Wiring Information Electrical Diagrams.

Theory of Operation

The intake air heater is integrated into the intake manifold cover. The air heater element is used to heat incoming air into the intake manifold. This is done to help engine starting and improve driveability with cool or cold outside temperatures. Electrical supply for the air heater element is controlled by the ECM through the air heater relay. One heavy duty cable connects the air heater element to the air heater relay. This cable will supply 12 volts to air heater elements. The ECM will light the MIL lamp as soon as this diagnostic runs and fails. The ECM will turn off the MIL lamp when the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
When the ignition is on.

- Set Condition:
When the signal from the Intake Air Heater output does not match the signal from the Intake Air Heater feedback.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure

1. RELAY CLICKING
1. Ignition on, engine not running.
2. With the scan tool, actuate the Intake Air Heater relay.

Can you hear the Relay clicking?

Yes

- Go To 2

No

- Go To 3

2. LOOSE CONNECTION
1. While the relay is clicking, wiggle the wiring harness and connectors.

Does this interrupt the clicking?

Yes

- Repair the poor connection.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Go To 3

3. INTAKE AIR HEATER RELAY
1. Turn the ignition off.
2. Remove the Intake Air Heater Relay.

NOTE: Check connectors - Clean/repair as necessary.

3. Measure the resistance between the signal and return posts of the intake air heater relay.

Is the resistance between 15 and 25 Ohms?

Yes

- Go To 4

No

- Replace the Intake Air Heater relay.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

4. SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE
1. Disconnect the ECM harness connector(s).

NOTE: Check connectors - Clean/repair as necessary.

2. Measure the resistance between the signal circuit of the intake air heater relay and battery negative.

Is the resistance greater than 100 K ohms?

Yes

- Go To 5

No

- Repair signal circuit shorted to battery negative.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

5. SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS
1. Measure the resistance between the signal circuit of the intake air heater relay and all other circuits in the ECM harness connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 6

No

- Repair signal circuit shorted to other circuits.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

6. ECM
1. Reconnect the ECM harness connectors.
2. Turn the ignition on.
3. Disconnect the intake air heater relay signal wire.

Did DTC P0542?

Yes

- Refer to the INTERMITTENT CONDITION - DIESEL (Diagnostic Procedure). Intermittent Condition Test

No

- Replace the ECM.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test