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FAULT CODE 234

Engine Overspeed

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Overview

CODE REASON EFFECT
Fault Code: 234
PID: P190
SPN: 190
FMI: 0
LAMP: Red
SRT: None		 Engine speed signal on pins 1 and 15 and/or pins 11 and 14 of the sensor harness connector indicated engine speed is greater than 2630 rpm. Fuel shutoff valve closed until engine speed falls to 2000 rpm.

Engine Position Sensor Circuit

Circuit Description

The engine position sensor (EPS) monitors engine position and engine speed, and passes this information to the electronic control module (ECM)
through the sensor harness.

Component Location

  • M11 – The EPS is located above the accessory drive.
  • N14 – The EPS is located at the back of the gear housing flange on the cylinder block, just above the lubrication pump.

Shop Talk

  • Inspect the engine position sensor for signs of damage or tampering.

Cautions and Warnings

 WARNING 

 

DO NOT OPERATE A DIESEL ENGINE WHERE THERE ARE OR CAN BE COMBUSTIBLE VAPORS. These vapors can be sucked through the air intake system and cause acceleration and overspeeding that can result in a fire, an explosion, and extensive property damage. Numerous safety devices are available, such as air intake shutoff devices, to minimize the risk of overspeeding where an engine, due to its application, might operate in a combustible environment, such as due to a fuel spill or gas leak. Remember, Cummins has no way of knowing the use you have for your engine. THE EQUIPMENT OWNER AND OPERATOR ARE RESPONSIBLE FOR SAFE OPERATION IN A HOSTILE ENVIRONMENT. CONSULT YOUR CUMMINS AUTHORIZED REPAIR LOCATION FOR FURTHER INFORMATION.
 CAUTION 

 

If the engine speed stays above 2630 rpm, the engine must be shut off immediately.
 CAUTION 

 

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

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Identify the reason for overspeed.
STEP 1A. Check for the proper operating conditions. Correct rpm reading; no damage
STEP 1B. Check for an alternate fuel source. No alternate fuel source
STEP 1C. Check for good vehicle grounding. Ground connections are clean and tight
STEP 1D. Check for moisture in ECM and connectors. All connectors are dry
STEP 1E. Inspect the harness and the sensor connector pins. No damaged pins
STEP 1F. Check the EPS for damage. No damage
STEP 1G. Check injector circuits and fuel shutoff solenoids for a short circuit to ground. Greater than 100k ohms
STEP 1H. Check datalink wiring. More than 100k ohms
STEP 1I. Check engine brake circuit for short circuit to ground. Greater than 100k ohms and correct engine or vehicle speed on service tool
STEP 1J. Check OEM components for shorting to ground. Greater than 100k ohms and correct engine or vehicle speed on service tool
STEP 1K. Check the alternator. Correct engine or vehicle speed on service tool
STEP 1L. Check other mechanical sources. Reset overhead; no overspeed
STEP 2. Clear the fault codes.
STEP 2A. Disable the fault code. Fault Code 234 inactive
STEP 2B. Clear the inactive fault codes. All fault codes cleared

Guided Step 1 – Identify the reason for overspeed.

Guided Step 1A – Check for the proper operating conditions.

Conditions

  • Turn keyswitch OFF.

Action

  • Check with the driver to determine if engine overspeeded past governed speed by more than 400 rpm.
  • Check if the engine was motoring downhill when the fault was logged.
  • Monitor the engine rpm using INSITE™ electronic service tool, while increasing speed to wide-open throttle slowly.
  • Note: Look at the snapshot data.
OK NOT OK
Correct rpm reading; no damage Engine overspeed

Check the engine for damage

Check the base engine for damage due to overspeed condition. Refer to the L10, M11, and N14 Engine Overspeed Manual, Bulletin 3666107, and repair.

 WARNING 

 

DO NOT OPERATE A DIESEL ENGINE WHERE THERE ARE OR CAN BE COMBUSTIBLE VAPORS. These vapors can be sucked through the air intake system and cause acceleration and overspeeding that can result in a fire, an explosion, and extensive property damage. Numerous safety devices are available, such as air intake shutoff devices, to minimize the risk of overspeeding where an engine, due to its application, might operate in a combustible environment, such as due to a fuel spill or gas leak. Remember, Cummins has no way of knowing the use you have for your engine. THE EQUIPMENT OWNER AND OPERATOR ARE RESPONSIBLE FOR SAFE OPERATION IN A HOSTILE ENVIRONMENT. CONSULT YOUR CUMMINS AUTHORIZED REPAIR LOCATION FOR FURTHER INFORMATION.
 CAUTION 

 

If the engine speed stays above 2630 rpm, the engine must be shut off immediately.
Guided Step 1B – Check for an alternate fuel source.

Conditions

  • Turn keyswitch OFF.

Action

  • Check if the driver reported a fuel-controlled event where the engine rapidly accelerated to or past 2600 rpm, followed by moderate deceleration to 2000 rpm.
  • Check the intake manifold for sources of flammable vapors and check the turbocharger seals to verify there are no oil leaks.
OK NOT OK
No alternate fuel source Remove alternate fuel sources

Locate any alternate fuel sources, such as operating the engine near flammable vapors, blown turbocharger seals, and so forth.

Guided Step 1C – Check for good vehicle grounding.

Conditions

  • Turn keyswitch OFF.

Action

  • Check from negative (-) battery post to block ground.
  • Check from block ground to negative (-) starter post ground.
  • Check block to frame ground.
  • Check block to cab ground.
  • Frame to (-) battery.
  • Cab to (-) battery.
OK NOT OK
Ground connections are clean and tight

Must measure within OEM specifications for voltage drop under electrical load

 Correct vehicle grounds.

Guided Step 1D – Check for moisture in ECM and connectors.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the sensor harness connector from the ECM.

Action

  • Check for moisture in the ECM connectors.
  • Check for moisture in the J1587 or J1922 datalink connectors.
  • Note : Typically, dash lamps will flash, injector solenoids will click, and the ECM will not communicate.
OK NOT OK
All connectors are dry Dry the connectors.

  • Dry the connectors by using electrical contact cleaner, Part Number 3824510.
  • Replace the connector seal. Refer to Procedure 019-203.

Guided Step 1E – Inspect the harness and the sensor connector pins.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness from the vehicle speed sensor.
  • Flush and clean the connector pins using electronic contact cleaner, Part Number 3824510.

Action

  • Bent or broken pins
  • Pushed back or expanded pins
  • Corroded pins
  • Moisture in or on the connector
  • Missing or damaged seals
  • Dirt or debris in or on the connector pins.
OK NOT OK
No damaged pins Repair the damaged pins

Flush the dirt, debris, or moisture from the connector pins. Repair or replace the OEM harness or the vehicle speed sensor, whichever has damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Repair or replace the OEM harness. Refer to the OEM troubleshooting and repair manual.
  • Replace the vehicle speed sensor. Refer to Procedure 019-091.

 CAUTION 

 

To reduce the possibility of damaging a new ECM, all other active fault codes must be investigated before replacing the ECM.
Guided Step 1F – Check the EPS for damage.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the sensor harness from the EPS.
  • Disconnect the sensor harness connector from the ECM.

Action

  • Electrical potting cracking
  • Metal shavings on end of sensor
  • Oil leakage or swelling or insulation
  • Damage to sensor from camshaft gear or flywheel.
OK NOT OK
No damage Replace the EPS.

Refer to Procedure 019-038.

Guided Step 1G – Check injector circuits and fuel shutoff solenoids for a short circuit to ground.

Conditions

  • Connect all components.
  • Disconnect actuator harness connector at the ECM.

Action

  • Check injector circuits for short circuit to ground.
  • Check fuel shutoff solenoid and associated circuits for a short circuit to ground.
OK NOT OK
Greater than 100k ohms

Correct engine or vehicle speed on service tool

 Less than 100k ohms

Incorrect engine or vehicle speed on service tool

Repair or replace component that failed.

Guided Step 1H – Check datalink wiring.

Conditions

  • Turn keyswitch OFF.
  • Disconnect sensor and OEM ECM connectors from ECM.

Action

  • Measure from pin 8 of the OEM connector at the ECM to engine block ground.
  • Measure from pin 27 of the OEM connector at the ECM to engine block ground.
  • Measure from pin 10 of the sensor connector at the ECM to engine block ground.
  • Measure from pin 20 of the sensor connector at the ECM to engine block ground.
  • Check OEM datalink power for shorts to ground, also.
OK NOT OK
More than 100k ohms Less than 100k ohms

Repair or replace datalink wiring

  • Repair the datalink wiring. Refer to Procedure 019-202.
  • Replace the engine harness. Refer to Procedure 019-043.
  • Replace the OEM harness. Refer to OEM manual for procedure.

Guided Step 1I – Check engine brake circuit for short circuit to ground.

Conditions

  • Disconnect engine brake connector from engine harness.
  • Turn keyswitch ON.

Action

  • Start engine.
  • Read service tool.
OK NOT OK
Greater than 100k ohms and correct engine or vehicle speed on service tool Repair or replace engine brake solenoids or engine brake harness

  • Repair the engine brake harness. Refer to Procedure 019-202.
  • Replace the engine brake harness. Refer to Procedure 019-043.
  • Replace the engine brake solenoid. Refer to the base engine troubleshooting and repair manual.

Guided Step 1J – Check OEM components for shorting to ground.

Conditions

  • Reconnect all components.

Action

  • Disable or unplug OEM components that can intermittently short to ground, such as fan clutch relays, keyswitch, engine speed sensors in the flywheel, tachographs, engine brakes, datalinks, OEM relays, vehicle speed sensors, or the alternator.
OK NOT OK
Greater than 100k ohms and correct engine or vehicle speed on service tool Repair or replace the OEM component

Refer to OEM manual for procedures.

Guided Step 1K – Check the alternator.

Conditions

  • Remove the alternator belt.
  • Connect the sensor harness to the ECM.

Action

  • Check vehicle speed or engine speed.
  • Start engine and let idle.
OK NOT OK
Correct engine or vehicle speed on service tool Repair or replace the alternator

NOTE: A capacitor across alternator output (observe proper polarity of capacitor) can help alternator-induced voltage spikes.

See manufacturer for specifications.

Guided Step 1L – Check other mechanical sources.

Conditions

  • Turn keyswitch OFF.

Action

  • Broken injector bias springs
  • Loose injector captive nuts
  • Plugged fuel tank vents
  • 12 VDC shorted to injectors.

NOTE: Run the automated cylinder performance test to identify the bad injectors and single-cylinder cutout test.

NOTE: Rough idle, smoke, or erratic rpm can be traced to a particular injector by taking temperature measurements on the exhaust manifold surface at each cylinder. Cylinders that are significantly higher than the cylinder adjacent to it at idle can have a malfunctioning injector. Maximum exhaust manifold surface temperature at idle is 143°C [290°F]. Tilting the exhaust manifold to identify excessive smoke in one cylinder compared to another is an additional method of locating a malfunctioning injector. Fuel knock in one cylinder caused by a malfunctioning cylinder can be picked out with the single-cylinder cutout test or by using a stethoscope.
OK NOT OK
Reset overhead; no overspeed Repair the damaged parts

Refer to these troubleshooting and repair manuals:

  • M11 Series Engines (STC, CELECT™, CELECT™ Plus models), Bulletin 3666139, until the fault goes inactive
  • N14 Series Engines (STC, CELECT™, CELECT™ Plus models), Bulletin 3666142, until the fault goes inactive

Guided Step 2 – Clear the fault codes.

Guided Step 2A – Disable the fault code.

Conditions

  • Connect all the components.

Action

  • Start the engine and let it idle for one minute.
  • Verify Fault Code 234 is inactive.
OK NOT OK
Fault Code 234 inactive Return to the troubleshooting steps or contact your nearest Cummins Authorized Repair Location if all the steps have been completed and checked again.

Guided Step 2B – Clear the inactive fault codes.

Conditions

  • Connect all the components.

Action

  • Erase inactive fault codes using INSITE™ electronic service tool.
OK NOT OK
All fault codes cleared Troubleshoot any remaining active fault codes.
Repair complete
Appropriate troubleshooting chart
Last Modified:  08-Sep-2004
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