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Electronic Control System Gas Plus Engines – FAULT CODE 488

Intake Manifold Temperature High – Over Temperature Warning

Overview

CODE REASON EFFECT
Fault Code: 488
PID: P105
SPN: 105
FMI: 0/16
LAMP: Amber
SRT: 

Intake Manifold Temperature High – Over Temperature Warning. High intake manifold temperature warning.

Progressive power derate increasing in severity from time of alert. If engine protection shutdown feature is enabled, engine will shut down 30 seconds after red stop light starts flashing.

Intake Manifold Temperature Sensor Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) uses the intake manifold pressure/temperature sensor input to determine the temperature of the intake manifold.

Component Location

The intake manifold pressure/temperature sensor is located in the intake manifold housing (combination sensor with absolute pressure).

Shop Talk

All temperature sensors:

  • The resistance of the sensor varies with temperature. The reading you observe must compare to the following table if the sensor is functioning properly.
Temperature (°C) Temperature [°F] Resistance (ohms)
0 32 30k to 36k
25 77 9k to 11k
50 122 3k to 4k
75 167 1350 to 1500
100 212 600 to 675
  • The engine protection shutdown for the intake manifold temperature is a customer feature and will only be enabled at the customer’s request. This feature will deactivate the fuel control valve if this feature is utilized by the OEM.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Read the fault codes. Fault Code 488 active?
STEP 2. Check the sensor accuracy.  
  STEP 2A. Verify the sensor accuracy with a thermocouple or similar probe. Temperature within five degrees?
STEP 3. Check the intake manifold pressure/temperature sensor.  
  STEP 3A. Inspect the intake manifold pressure/temperature sensor and engine harness connector pins. Dirty or damaged pins?
  STEP 3B. Read the fault codes. Fault Code 488 active?
STEP 4. Clear the fault codes.  
  STEP 4A. Disable the fault code. Fault Code 488 inactive?
  STEP 4B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check the fault codes.

Guided Step 1A – Read the fault codes.

Conditions

  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 488 active?
YES NO
No Repair No Repair

Guided Step 2 – Check the sensor accuracy.

Guided Step 2A – Verify the sensor accuracy with a thermocouple or similar probe.

Conditions

  • Connect INSITE™ electronic service tool
  • Turn keyswitch ON.

Action

  • Compare the intake manifold temperature reading on INSITE™ electronic service tool to the reading from the probe.

Note: If no temperature measuring device is available, answer Yes to this step.

Temperature within five degrees?
YES NO
No Repair

Replace the sensor. Refer to Procedure 019-099.

Guided Step 3 – Check the intake manifold pressure/temperature sensor.

Guided Step 3A – Inspect the intake manifold pressure/temperature sensor and engine harness connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the intake manifold pressure/temperature sensor.

Action

  • Corroded pins
  • Bent or broken pins
  • Pushed back or expanded pins
  • Wire insulation damage
  • Moisture in or on the connector
  • Missing or damaged connector seals
  • Connector shell broken
  • Dirt or debris in or on the connector pins.

For general inspection techniques, refer to Component Connector and Pin Inspection, Procedure 019-361.

Dirty or damaged pins?
YES NO

Repair the damaged pins. Repair or replace the engine harness, or replace the sensor, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Install the appropriate connector seal if it is damaged or missing.
  • Repair the harness. Refer to Procedure 019-205.
  • Replace the harness. Refer to Procedure 019-043.
  • Replace the ICM. Refer to Procedure 019-099.
 No Repair

Guided Step 3B – Read the fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Start the engine and let it idle for one minute.
  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 488 active?
YES NO

Refer to the Intake Manifold Temperature Above Normal troubleshooting tree in the Troubleshooting and Repair Manual C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

 No Repair

Guided Step 4 – Clear the fault codes.

Guided Step 4A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Start the engine and let it idle for one minute.
  • Use INSITE™ electronic service tool to verify that Fault Code 488 is inactive.

Fault Code 488 inactive?
YES NO
No Repair

Troubleshooting procedures need to be repeated from the beginning.

Guided Step 4B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to erase the inactive fault codes.

All fault codes cleared?
YES NO
No Repair

Troubleshoot any remaining active fault codes.
Repair complete
Appropriate troubleshooting charts
Last Modified:  22-Sep-2004
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