P154A

DTC P154A

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptor

DTC P154A
- Intake Air (IA) Heater Feedback Circuit

Diagnostic Fault Information






Circuit/System Description

The intake air heater (IAH) is located in the air inlet tube and is used to warm the incoming air to aid in starting the engine and for proper cylinder combustion. The glow plug control module (GPCM) will command the IAH on when the engine coolant temperature is below 40°C (104°F). Power to the IAH is supplied by the battery positive voltage circuit. The IAH is connected to the GPCM by the following circuits. If there is a fault on any of these circuits a DTC will set.

* The IAH temperature signal circuit
* The IAH command 1 circuit
* The IAH command 2 circuit
* The IAH voltage signal circuit
* The IAH current signal circuit
* The IAH feedback signal circuit

Conditions for Running the DTC

* The IAH is commanded ON
* The IAH battery voltage is more than 8.6 volts.
* DTCs P154A runs continuously when the above condition is met.

Conditions for Setting the DTC

The digital response signal is low and the IAH current is high.

Action Taken When the DTC Sets

DTC P154A is a Type B DTC.

Conditions for Clearing the DTC

DTC P154A is a Type B DTC.

Circuit/System Verification

Important: If you cannot duplicate the condition, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

1. Observe that the IAH Feedback Circuit Low parameter displays NO
2. Observe that the IAH Driver Shorted parameter displays OK.
3. Engine running, observe the DTC information with a scan tool. DTC P154A should not set.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame Records data.

Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Test the IAH feedback signal circuit for an open, a short to ground, or a short to voltage

• If a condition is found, repair a necessary.

Important: Set the DMM to the 4 v AC hertz scale.

2. With a DMM measure between command 2 circuit terminal 3 and a good ground on the harness side of the connector for 0.78-1.1 Hz.

• If the DMM does not measure between 0.78-1.1 Hz ohms, replace the GPCM.

Important:
* Do not install the jumper wire between 12 volts and the command circuit for more the 20 seconds.

* Set the DMM to the 4 v AC hertz scale.

Turn OFF the ignition. Install a jumper wires between the IAH and the IAH harness for the temperature signal circuit terminal 1 and between the IAH and the IAH harness command 2 circuit terminal 3. Install a jumper wire between 12 volts and the command 1 terminal 2 on the IAH. Turn ON the ignition. With a DMM measure for 1 hertz on the Feedback signal circuit

• If the DMM measures 0.7-1.1 hertz for the Feedback signal circuit, replace the GPCM.
• If the DMM does not measure 0.7-1.1 hertz for the Feedback signal circuit, replace the IAH.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Control Module References for GPCM replacement, setup, and programming Programming and Relearning
* Intake Air Heater Replacement