VIN 6
DTC P154B
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (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). The IAH is connected to the GPCM by the following circuits:
* 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
If there is a fault on any of these circuits, a DTC will set.
Power to the IAH is supplied by the battery positive voltage circuit. An open/high resistance or a short to ground on this circuit will also set DTC P154B.
Conditions for Running the DTC
* The IAH is commanded ON.
* The GPCM battery voltage is between 9.5-15 volts.
* DTC P154B runs continuously when the above condition is met.
Conditions for Setting the DTC
Voltage at the IAH voltage signal is 16 volts or more.
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.
Diagnostic Aids
A loose connection on the battery positive voltage circuit terminal 1 X2 of the IAH, or at the 175A Mega Fuse terminal 1 X4 of the Underhood Fuse Holder, may cause this DTC to set.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Intake Air Heater System Description (Intake Air Heater System Description)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. With the ignition ON, observe that the IA Heater Undervoltage parameter displays OK. Observe that the IAH volts displays near ignition 1 signal volts.
2. Observe that the IAH can be commanded 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. Connect a test lamp between the battery positive voltage circuit terminal 1 X2 at the IAH and ground. The test lamp should illuminate.
• If the test lamp does not illuminate, test the circuit for an open/high resistance or a short to ground and repair as necessary.
2. Test the following circuits for an open, a short to ground, or a short to voltage:
* The IAH command 1 circuit between terminal 31 X2 of the GPCM and terminal 2 X1 of the IAH
* The IAH command 2 circuit between terminal 26 X2 of the GPCM and terminal 3 X1 of the IAH
* The IAH voltage signal circuit between terminal 30 X2 of the GPCM and terminal 5 X1 of the IAH
• If a condition was found on any of the circuits repair as necessary.
3. Connect any circuits that were disconnected. With the ignition ON and the engine OFF, observe that the scan tool displays the IA Heater Undervoltage parameter as OK.
• If the IA Heater Undervoltage parameter displays Fault, replace the intake air heater.
• If the IA Heater Undervoltage parameter does not display Fault, replace the GPCM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Intake Air Heater Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for GPCM replacement, setup, and programming