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Electronic Control System Gas Plus Engines – FAULT CODE 178

Electronic Throttle Control Actuator – Stuck Closed

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Overview

Electronic Throttle Control Actuator – Stuck Closed

CODE REASON EFFECT
Fault Code: 178
PID: S58
SPN: 698
FMI: 7
LAMP: Red
SRT: 

Electronic Throttle Control Actuator – stuck closed. The throttle plate has moved unexpectedly.

Possible reduced performance. Engine may die or not start.

Electronic Throttle Control Actuator Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) controls the electronic throttle control actuator; it is both an input and output device.

Component Location

The electronic throttle control actuator is located after the fuel housing and before the intake manifold inlet.

Shop Talk

The Electronic Throttle Control Actuator is a pulse-width modulated component. Within the actuator is the throttle position sensor circuit. This is a non-repairable sensor and requires replacement of the actuator upon failure.

Cautions and Warnings

 CAUTION 

To reduce the possibility of damaging a new ECM, all other active fault codes must be investigated prior to replacing the ECM.
 CAUTION 

To reduce the possibility of pin and harness damage, use the appropriate test leads when taking a measurement.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Read the fault codes. Fault Code 178 active?
STEP 2. Check the throttle actuator.  
  STEP 2A. Inspect the throttle actuator and engine harness connector pins. Damaged or dirty pins?
  STEP 2B. Read the fault codes. Fault Code 178 active?
STEP 3. Verify the throttle operation.  
  STEP 3A. Verify the throttle operation. Did the gas throttle control pass the test?
STEP 4. Check the engine harness.  
  STEP 4A. Inspect the engine harness and ECM connector pins. Damaged or dirty pins?
  STEP 4B. Read the fault codes. Fault Code 178 active?
  STEP 4C. Check for an open circuit. Less than 10 ohms?
  STEP 4D. Check for a short circuit to ground. More than 100k ohms?
  STEP 4E. Check for a short circuit from pin to pin. More than 100k ohms?
  STEP 4F. Check the throttle actuator for an obstruction or damage. Obstruction or damage?
STEP 5. Clear the fault codes.  
  STEP 5A. Disable the fault code. Fault Code 178 inactive?
  STEP 5B. 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

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

Read the fault codes.

Fault Code 178 active?
YES NO
No Repair No Repair

Guided Step 2 – Check the throttle actuator.

Guided Step 2A – Inspect the throttle actuator and engine harness connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the throttle actuator.

Action

Inspect the actuator and engine harness 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
  • Connector shell broken
  • Wire insulation damage
  • Damaged locking tab connector.

Damaged or dirty pins?
YES NO

Repair or replace the engine harness, or replace the actuator, 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 019-201.
  • Replace the engine harness. Refer to Procedure 019-043.
  • Replace the actuator. Refer to Procedure 019-097.
 No Repair

Guided Step 2B – Read the fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON.

Action

Read the fault codes.

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

Fault Code 178 active?
YES NO
No Repair No Repair

Guided Step 3 – Verify the throttle operation.

Guided Step 3A – Verify the throttle operation.

Conditions

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

Action

Verify proper throttle operation.

  • Use INSITE™ electronic service tool to activate the gas throttle control test.

Did the gas throttle control pass the test?
YES NO
No Repair

Replace the throttle actuator. Refer to Procedure 005-052 in the Troubleshooting and Repair Manual C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206, or Procedure 005-052 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164

Guided Step 4 – Check the engine harness.

Guided Step 4A – Inspect the engine harness and ECM connector pins.

Conditions

  • Turn the keyswitch OFF
  • Disconnect the engine harness from the ECM.

Action

Inspect the engine harness and ECM 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
  • Connector shell broken
  • Wire insulation damage
  • Damaged locking tab connector.

Damaged or dirty pins?
YES NO

Repair or replace the engine harness, or replace the ECM, 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 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.
  • Replace the ECM. Call for pre-authorization. Refer to Procedure 019-031.
 No Repair

Guided Step 4B – Read the fault codes.

Conditions

  • Connect all components
  • Turn the keyswitch ON.

Action

Read the fault codes.

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

Fault Code 178 active?
YES NO
No Repair No Repair

Guided Step 4C – Check for an open circuit.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the throttle actuator
  • Disconnect the engine harness from the ECM.

Action

Check for an open circuit.

  • Measure the resistance from the throttle position (+) pin in the engine harness connector to the throttle position (+) pin in the engine harness actuator connector.
  • Measure the resistance from the throttle actuator (+) pin in the engine harness connector to the throttle actuator (+) pin in the engine harness actuator connector.
  • Measure the resistance from the throttle position (-) pin in the engine harness connector to the throttle position (-) pin in the engine harness actuator connector.
  • Measure the resistance from the throttle actuator (-) pin in the engine harness connector to the throttle actuator (-) pin in the engine harness actuator connector.
SMALL | MEDIUM | LARGE

Less than 10 ohms?
YES NO
No Repair

Repair or replace the engine harness.

  • Repair the engine harness. Refer to Procedure 019-201 or 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 4D – Check for a short circuit to ground.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the throttle actuator.
  • Disconnect the engine harness from the ECM.

Action

Check for a short circuit to engine block ground.

  • Measure the resistance from the throttle position (+) pin in the engine harness ECM connector to engine block ground.
  • Measure the resistance from the throttle actuator (+) pin in the engine harness ECM connector to engine block ground.
  • Measure the resistance from the throttle position (-) pin in the engine harness ECM connector to engine block ground.
  • Measure the resistance from the throttle actuator (-) pin in the engine harness ECM connector to engine block ground.
SMALL | MEDIUM | LARGE

More than 100k ohms?
YES NO
No Repair

Repair or replace the engine harness.

  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 4E – Check for a short circuit from pin to pin.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the throttle actuator.
  • Disconnect the engine harness from the OEM harness at the 23 pin and 31 pin OEM connectors.
  • Disconnect engine harness connector 1 and connector 2 from the ECM.

Action

Check for a short circuit from pin to pin.

  • Measure the resistance from the throttle position (+) pin in engine harness connector 1 and all pins in engine harness ECM connector 2.
  • Measure the resistance from the throttle actuator (+) pin in engine harness connector 1 and all pins in engine harness ECM connector 2.
  • Measure the resistance from the throttle position (-) pin in engine harness connector 1 and all pins in engine harness ECM connector 2.
  • Measure the resistance from the throttle actuator (-) pin in engine harness connector 1 and all pins in engine harness ECM connector 2.
SMALL | MEDIUM | LARGE

More than 100k ohms?
YES NO
No Repair

Repair or replace the engine harness.

  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 4F – Check the throttle actuator for an obstruction or damage.

Conditions

  • Turn keyswitch OFF.

Action

Inspect the throttle actuator for an obstruction or damage.

  • Check the throttle plate for straightness. If the plate is bent, replace the throttle actuator.

Obstruction or damage?
YES NO

Replace the throttle actuator. Refer to Procedure 005-052 in the Troubleshooting and Repair Manual C Gas, C Gas Plus, and L Gas Plus Engines, bulletin 3666206, or Procedure 005-052 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164

 No Repair

Guided Step 5 – Clear the fault codes.

Guided Step 5A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON.

Action

Disable the fault code.

  • Start the engine and let it idle for one minute.
  • Verify that Fault Code 178 is inactive.

Fault Code 178 inactive?
YES NO
No Repair

Return to troubleshooting steps or contact a local Cummins® authorized repair location if all steps have been completed and checked again.

Guided Step 5B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON.

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 fault codes.
Repair complete
Appropriate troubleshooting charts
Last Modified:  12-May-2005
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