P154B
DTC P154B
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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
1. With the ignition ON, observe that the IA Heater under voltage 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/Failure 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 voltage 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 parameter as OK.
^ If the IA Heater Driver Shorted 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 parameter as OK.
^ If the Glow Plug Driver Shorted parameter displays Fault, replace the Glow Plug Control Module.
Important: Set the DMM to the 4V DC hertz scale.
4. Disconnect the IAH. Turn ON the ignition. 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 4V AC hertz scale.
Turn OFF the ignition. Install a jumper wire between the IAH harness temperature signal circuit terminal 1 and the corresponding terminal on the IAH.
5. Install a jumper wire between the IAH harness command two circuit terminal 3 and the corresponding terminal on the IAH.
6. Supply 12 volts to terminal 2 on the IAH.
7. Turn ON the ignition. Measure for 1 hertz on terminal 5 at the IAH.
^ If 0.7-1.1 hertz is measured on terminal 5, replace the GPCM.
^ If 0.7-1.1 hertz is not measured on terminal 5, replace the IAH.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Intake Air Heater Replacement