VIN L
DTC P154C
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 P154C
- Intake Air (IA) Heater Current Signal Circuit.
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The intake air heater is located in the air inlet tube and is used to warm the incoming air to aid in cylinder combustion during cold weather operation. The engine control module (ECM) sends commands to the glow plug control module to enable or disable the intake air heater when certain conditions met. The glow plug control module monitors the voltage and feedback circuits of the intake air heater to verify proper operation. If the Intake Air Heater Current Feedback Signal circuit is opened, shorted to voltage, or shorted to ground DTC P154C may set.
Conditions for Running the DTC
* The intake air heater is commanded ON.
* The intake air heater battery voltage is more than 6.9 V.
* Glow plug control module ignition voltage is more than 6.9 V.
* DTC P154C runs continuously when the above conditions are met.
Conditions for Setting the DTC
DTC will set when any of the following conditions exists.
* Intake air heater current is less the 20 A when the duty cycle is high for more than 320 ms.
* Intake air heater current is out of range when the duty cycle is commanded low for more than 5000 ms.
* The Intake Air Heater Current Feedback Signal voltage is greater than 4.96 V for more than 650 ms.
* The glow plug control module determines the intake air heater resistance is greater than 500 ohm when current flow is greater than 20 A for more than 160 ms.
Action Taken When the DTC Sets
DTC P154C is a Type B DTC.
Conditions for Clearing the DTC
DTC P154C 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)
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. Engine running, command the intake air heater ON and OFF with a scan tool while observing the IA Htr Current Sig Ckt. Status parameter.
The IA Htr Current Sig Ckt. Status parameter should display OK.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
1. Test the Intake Air Heater Current Feedback Signal circuit between the intake air heater terminal 4 X1 and glow plug control module terminal 16 X2 for an open, a short to ground, or a short to voltage.
• If a condition is found, repair as necessary.
2. Ignition OFF, disconnect the X1 harness connector of the intake air heater. Connect any other circuits that were previously disconnected.
Note: Set the DMM to the 4V DC hertz scale.
3. Ignition ON, with a scan tool command the intake air heater OFF, measure the frequency between the Intake Air Heater Heart Beat Signal circuit terminal 3 of the intake air heater X1 connector and ground. The frequency should be 0.78-1.1 Hz.
• If not within the specified range, replace the K34 glow plug control module.
Note:
* Do not supply B+ to terminal 2 on the intake air heater for more than 20 seconds.
* Set the DMM to the 4V DC hertz scale.
4. Turn OFF the ignition. Install a jumper wire between temperature signal circuit terminal 1 of the intake air heater X1 connector and the corresponding terminal on the intake air heater.
5. Install a jumper wire between the Intake Air Heater Heart Beat Signal circuit terminal 3 of the intake air heater X1 connector and the corresponding terminal on the intake air heater.
6. Supply B+ to the Intake Air Heater Switch On/Off Signal circuit terminal 2 on the intake air heater.
7. Ignition ON, measure the frequency between the Intake Air Heater Current Feedback Signal circuit terminal 4 at the intake air heater and ground. The frequency should be 0.7-1.1 Hz.
• If within the specified range, replace the K34 glow plug control module.
• If not within the specified range, replace the E24 intake air heater.
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 glow plug control module replacement, programming, and setup