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Electronic Control System Gas Plus Engines – FAULT CODE 124 – B and C Gas Plus

High Mixer Inlet Pressure – Overboost

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Overview

CODE REASON EFFECT
Fault Code: 124
PID: P102
SPN: 102
FMI: 0/16
LAMP: Amber
SRT: 

High mixer inlet pressure – Overboost. Pressure is above the engine protection limit.

Engine power derate.

Mixer Inlet Pressure Sensor Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The Mixer Inlet Pressure Sensor measures the inlet air pressure entering the fuel housing.

Component Location

The Mixer Inlet Pressure Sensor is located in the air inlet elbow.

Shop Talk

The Mixer Inlet Pressure Sensor detects the pressure of the air entering the mixer housing. This is sometimes referred to as the boost pressure sensor or compressor outlet pressure sensor. If the Mixer Inlet Pressure Sensor is disconnected, the engine can continue operating by using the accelerator plate position and the manifold absolute pressure to estimate the mixer inlet pressure. Before performing any wiring checks, disconnect the sensor from the engine harness.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Read the fault codes. Fault Codes 122 or 123 active?
STEP 2. Check the Mixer Inlet Pressure Sensor.  
  STEP 2A. Inspect the engine harness and Mixer Inlet Pressure Sensor connector pins. No damaged pins
  STEP 2B. Verify the mixer inlet pressure. Mixer inlet and manifold absolute pressure values the same at atmospheric pressure?
  STEP 2C. Read the fault codes. Fault Code 124 active?
STEP 3. Check the mechanical components.  
  STEP 3A. Check the turbocharger. Turbocharger is correct and is operating correctly?
  STEP 3B. Check the air intake restriction. Is restriction within specification?
STEP 4. Clear the fault codes.  
  STEP 4A. Disable the fault code. Fault Code 124 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 the INSITE™ electronic service tool.

Action

Read the fault codes.

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

Fault Codes 122 or 123 active?

YES NO

Troubleshoot Fault Codes 122 or 123.

 No Repair
Appropriate troubleshooting tree

Guided Step 2 – Check the Mixer Inlet Pressure Sensor.

Guided Step 2A – Inspect the engine harness and Mixer Inlet Pressure Sensor connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the Mixer Inlet Pressure Sensor.

Action

Inspect the engine harness and mixer inlet pressure sensor connector pins for the following:

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

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

Damaged or dirty 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 engine harness. Refer to Procedure
    019-202.
  • Replace the engine harness. Refer to Procedure
    019-043.
  • Replace the sensor. Refer to Procedure
    019-098.
 No Repair

Guided Step 2B – Verify the mixer inlet pressure.

Conditions

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

Action

Check the mixer inlet pressure with INSITE™ electronic service tool.

  • Use INSITE™ electronic service tool to compare the mixer inlet pressure and manifold absolute pressure.

Mixer inlet and manifold absolute pressure values the same at atmospheric pressure?
YES NO
No Repair

Replace the Mixer Inlet Pressure Sensor. Refer to Procedure
019-098.

Guided Step 2C – Read the fault codes.

Conditions

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

Action

Read the fault codes.

  • Start the engine and let it idle for 1 minute.
  • Read the fault codes with INSITE™ electronic service tool.

Fault Code 124 active?
YES NO
No Repair No Repair

Guided Step 3 – Check the mechanical components.

Guided Step 3A – Check the turbocharger.

Conditions

  • Turn keyswitch OFF.

Action

Check the turbocharger.

  • Confirm that the turbocharger is the correct one.
  • Check the turbocharger and wastegate plumbing for mechanical problems. Refer to Procedure
    010-050 in the Troubleshooting and Repair Manual, C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206, and Procedure
    010-050 in the Troubleshooting and Repair Manual, B5.9G, B5.9LPG, B Gas Plus, B LPG Plus, B Gas International, and G5.6 Engines, Bulletin 3666164.

Turbocharger is correct and is operating correctly?
YES NO
No Repair

Repair or replace the turbocharger wastegate.

  • Refer to Procedure
    010-050 in the Troubleshooting and Repair Manual, C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206, and Procedure
    010-050 in the Troubleshooting and Repair Manual, B5.9G, B5.9LPG, B Gas Plus, B LPG Plus, B Gas International, and G5.6 Engines, Bulletin 3666164.

Guided Step 3B – Check the air intake restriction.

Conditions

  • Turn keyswitch OFF.

Action

Check the air intake restriction.

  • Check the intake restriction of the engine. Refer to Procedure
    010-031 in the Troubleshooting and Repair Manual, C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206, Bulletin 3666206, and Procedure
    010-031 in the Troubleshooting and Repair Manual B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164.

Is restriction within specification?
YES NO
No Repair

Correct the restriction. Remove the restriction or replace the air cleaner element. Refer to Procedure
010-031 in the Troubleshooting and Repair Manual, C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206, Bulletin 3666206, and Procedure
010-031 in the Troubleshooting and Repair Manual B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164.

Guided Step 4 – Clear the fault codes.

Guided Step 4A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON.

Action

Disable the fault code.

  • Start the engine and let it idle for 1 minute.
  • Verify that Fault Code 124 is inactive.

Fault Code 124 active?
YES NO

Troubleshooting procedures need to be repeated from the beginning.

 No Repair

Guided Step 4B – Clear the inactive fault codes.

Conditions

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

Action

Clear the inactive fault codes.

  • 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:  05-Jan-2007
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