P154B

DTC P154B

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 P154B
- Intake Air (IA) Heater Voltage Signal 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.
* DTCs P154B runs continuously when the above conditions are met.

Conditions for Setting the DTC

* IAH battery voltage is more than 16 volts.
* The GPCM battery voltage is between 8-16 volts.

Action Taken When the DTC Sets

DTC P154B is a Type B DTC.

Conditions for Clearing the DTC

DTC P154B 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. With the ignition ON, observe that the IA Heater undervoltage parameter displays OK
2. Observe that the IAH can be command ON with a scan tool.
3. Engine running, observe the DTC information with a scan tool. DTC P154B 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 following circuits for an open, a short to ground, or a short to voltage:

* The IAH command 1 circuit
* The IAH command 2 circuit
* The IAH current signal circuit

• If a condition was found on any of the circuits repair as necessary.

2. Connect any circuits that were disconnected. With the ignition ON and the engine OFF, observe that the scan tool displays the IA Heater Driver Shorted Open parameter as OK.

• If the IA Heater Driver Shorted Open parameter displays Fault, replace the intake air heater.

3. With the ignition ON and the engine OFF, observe that the scan tool displays the Glow Plug Driver Shorted Open parameter as OK.

• If the Glow Plug Driver Shorted Open parameter displays Fault, replace the Glow Plug Control Module.

4. With the ignition ON and the engine OFF, observe the GPCM data display with a scan tool.

• If the glow plug undervoltage displays Fault, and the IA heater undervoltage displays OK, replace the GPCM.
• If the glow plug overvoltage displays Fault, and the IA heater overvoltage as OK, replace the GPCM.
• If the glow plug undervoltage displays OK, and the IA heater undervoltage displays Fault, replace the IAH.
• If the scan tool displays the glow plug overvoltage as OK, and the IAH overvoltage as Fault, replace the IAH.

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

5. 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 command 2 circuit terminal 3. Install a jumper wire between 12 volts and the command 1 terminal on the IAH. Turn ON the ignition. With a DMM measure for 1 hertz on the current signal circuit:

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