VIN 6
DTC P154D
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 P154D
- Intake Air (IA) Heater Temperature 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.
* The IAH battery voltage is between 6.9-16 volts.
* DTC 154D runs continuously when the above conditions are met.
Conditions for Setting the DTC
The GPCM detected an open, short to ground or short to battery on the IAH temperature signal circuit.
Action Taken When the DTC Sets
DTC P154D is a Type B DTC.
Conditions for Clearing the DTC
DTC P154D is a Type B DTC.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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
Observe the following with a scan tool.
1. The IAH Temp CKT Status parameter should display OK.
2. The IAH can be commanded ON with a scan tool.
3. Engine running, observe the DTC information with a scan tool. DTC P154D 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. Ignition OFF, disconnect the X1 harness connector of the IAH.
2. Turn ON the ignition and measure between temperature signal circuit terminal 1 of the connector and a good ground for 2-3 volts.
• If greater than the specified range, test the temperature signal circuit for a short to voltage. If the circuit tests normal, replace the GPCM.
• If less than the specified range, test the temperature signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the GPCM.
3. If the temperature signal circuit tests normal, replace the IAH.
Component Testing
Disconnect the IAH and measure between the temperature signal circuit terminal 1 on the IAH and a good ground for 15,000-18,000 ohms with a DMM.
If the DMM does not measure between 15,000-18,000 ohms, replace the IAH.
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