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FAULT CODE 241

Vehicle Speed Sensor (VSS) Circuit

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Overview

CODE REASON EFFECT
Fault Code: 241
PID: P084
SPN: 84
FMI: 2
LAMP: Yellow
SRT: 00-097		 Lost vehicle speed signal on pins 3 and 7 of the OEM harness connector or pin 7 and ground on the OEM harness connector. Engine speed limited to “Maximum Vehicle Speed without Vehicle Speed Sensor” parameter value.

Vehicle Speed Sensor Circuit

Circuit Description

The vehicle speed sensor (VSS) uses two separate coils of wire to count gear teeth as they pass in front of the sensor. One coil is used by the electronic control module (ECM) to sense vehicle speed. The other coil is sometimes used by the OEM to send a vehicle speed signal to the speedometer.

Component Location

The VSS is installed in the rear of the transmission.

Shop Talk

  • The vehicle must be moved before Fault Code 241 will go inactive.
  • Not all VSS manufacturers meet the Cummins VSS specifications by using a 750-ohm to 1500-ohm coil. They can vary the resistance, number of turns, wire size, and so on to generate proper electrical parameters for the VSS.
  • Do not replace the VSS without checking the specification for those sensors of an alternate design.
  • The variable reluctance (magnetic pickup) style of VSS can not tolerate two loads in the same circuit. This is the reason for two coils in one sensor. One coil circuit feeds the ECM and the other feeds the speedometer. Any additional loads on a single coil will cause Fault Code 241. Check for additional loads.
  • A single-coil VSS used in some applications, e.g., automatic transmissions, will feed a conditioning circuit that outputs a digital speed signal to ECM pin 7.

Note: ECM pin 3 is not used in this type of circuit and must be vacated. Again, no additional loads can be spliced into the VSS between the sensor and conditioning circuit or vehicle interface module.

  • The digital signal from the vehicle interface module conditioning circuit can feed multiple devices, such as the ECM and the speedometer, simultaneously, since it has been properly conditioned for this purpose.
  • Verify the VSS wires in the OEM harness are twisted pairs.
  • Fault Code 241 becomes active only if the ECM receives a speed signal and then loses the signal. The fault will not go active if it never received one; e.g., the VSS is unplugged. The fault will go inactive once it picks up a speed signal again.
  • Electrical noise or drivetrain vibration can simulate a VSS signal sitting still; therefore, when the vibration or electrical noise dissipates, the fault can go active; i.e., the ECM had a valid signal but lost it.

Cautions and Warnings

 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test leads when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead
Part Number 3823996 – female Weather-Pack test lead.
 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 following test lead when taking a measurement:
Part Number 3823996 – female Weather-Pack test lead.
 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the VSS.
STEP 1A. Inspect the harness and the sensor connector pins. No damaged pins
STEP 1B. Read the fault codes. Fault Code 241 active
STEP 1C. Check the VSS for proper adjustment. 1/2 to 3/4 of a turn out from the gear
STEP 1D. Inspect the harness and the ECM connector pins. No damaged pins
STEP 1E. Read the fault codes. Fault Code 241 active
STEP 1F. Check the VSS for the correct resistance. 750 to 1500 ohms or meets OEM specification
STEP 1G. Check the VSS for a short circuit to ground. More than 100k ohms
STEP 1H. Check the VSS for a short circuit between coils. More than 100k ohms
STEP 2. Check the OEM harness.
STEP 2A. Check the harness for a short circuit to ground. More than 100k ohms
STEP 2B. Check the harness for a short circuit from pin to pin. More than 100k ohms
STEP 3. Check the OEM components.
STEP 3A. Check for an external recording device. No external device
STEP 3B. Check for a gear slipping on the shaft. Gear attached properly
STEP 4. Check for electrical interference.
STEP 4A. Check vehicle speed. No vehicle speed; vehicle parked
STEP 4B. Check for good vehicle grounding. Ground connections are clean and tight
STEP 4C. Check vehicle speed with the ECM away from the engine block. No vehicle speed on electronic service tool
STEP 4D. Check alternator. No vehicle speed on electronic service tool
STEP 4E. Check other OEM components for shorting to ground. No vehicle speed on the electronic service tool
STEP 4F. Check engine brake circuit. No vehicle speed on the electronic service tool
STEP 4G. Check datalink wiring for short circuit to ground. More than 100k ohms
STEP 4H. Check injector circuits and fuel shutoff solenoids for short circuit to ground. More than 100k ohms and no vehicle speed on the electronic service tool
STEP 4I. Check for electromagnetic induction noise or feedback from another device on VSS circuit. Vehicle parked; no vehicle speed on service tool
STEP 4J. Check for vehicle speed with VSS disconnected. Vehicle parked; no vehicle speed
STEP 5. Clear the fault codes.
STEP 5A. Disable the fault code. Fault Code 241 inactive
STEP 5B. Clear the inactive fault codes. All fault codes cleared

Guided Step 1 – Check the VSS.

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

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness from the VSS.
  • 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 using electronic contact cleaner, Part Number 3824510.
  • Repair the OEM harness. Refer to Procedure 019-201, 019-202, or 019-205.
  • Replace the OEM harness. Refer to the OEM troubleshooting and repair manual.
  • Replace the VSS. Refer to Procedure 019-090 or 019-091.

Guided Step 1B – Read the fault codes.

Conditions

  • Turn keyswitch OFF.
  • Connect all components.

Action

  • Start the engine and move the vehicle.
  • Read the fault codes using INSITE™.
OK NOT OK
Fault Code 241 active Repair complete.

Guided Step 1C – Check the VSS for proper adjustment.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness from the VSS.

Action

  • Check the VSS for proper adjustment.

Note: This can vary for a VSS that is designed to have a different resistance value than shown in this tree and on the wiring diagram. Check with the OEM.
OK NOT OK
1/2 to 3/4 of a turn out from the gear Adjust the VSS. Refer to Procedure 019-090 or 019-091.

 CAUTION 

 

To reduce the possibility of damaging a new ECM, all other active fault codes must be investigated prior to replacing the ECM.
Guided Step 1D – Inspect the harness and the ECM connector pins.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness connector from the ECM.
  • 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 using electronic contact cleaner, Part Number 3824510.
  • Repair the OEM harness. Refer to Procedure 019-203.
  • Replace the OEM harness. Refer to the OEM troubleshooting and repair manual.
  • Replace the ECM. Refer to Procedure 019-031.
  • Replace the o-ring on the 28-pin connector if it is damaged or missing. Refer to Procedure 019-203.

Guided Step 1E – Read the fault codes.

Conditions

  • Turn keyswitch OFF.
  • Connect all components.

Action

  • Start the engine and move the vehicle.
  • Read the fault codes using INSITE™.
OK NOT OK
Fault Code 241 active Repair complete.

 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3823996 – female Weather-Pack test lead.
Guided Step 1F – Check the VSS for the correct resistance.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness from the vehicle speed sensor.

Action

  • Measure the resistance from pin A to pin B for each VSS connector on the sensor side.

Note: See the OEM for the required resistance of a VSS designed outside of Cummins recommendations.
OK NOT OK
750 to 1500 ohms or meets OEM specification Replace the VSS. Refer to Procedure 019-090 or 019-091.

 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3823996 – female Weather-Pack test lead.
Guided Step 1G – Check the VSS for a short circuit to ground.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness from the vehicle speed sensor.

Action

  • Measure the resistance between pin A on the sensor side of one of the VSS connectors and the engine block ground.
  • Measure the resistance between pin A on the sensor side of the other VSS connector and the engine block ground.
OK NOT OK
More than 100k ohms Replace the VSS. Refer to Procedure 019-090 or 019-091.

 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3823996 – female Weather-Pack test lead.
Guided Step 1H – Check the VSS for a short circuit between coils.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness from the VSS.

Action

  • Measure the resistance between pin B on the sensor side of one of the VSS connectors and pin B of the other connector.
OK NOT OK
More than 100k ohms Replace the VSS. Refer to Procedure 019-090 or 019-091.

Guided Step 2 – Check the OEM harness.

 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead.
Guided Step 2A – Check the harness for a short circuit to ground.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness from the VSS.
  • Disconnect the OEM harness connector from the ECM.

Action

  • Measure the resistance from pin 3 of the OEM harness connector to engine block ground.
  • Measure the resistance from pin 7 of the OEM harness connector to engine block ground.
OK NOT OK
More than 100k ohms Repair or replace the OEM harness. Refer to the OEM troubleshooting and repair manual.

 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead.
Guided Step 2B – Check the harness for a short circuit from pin to pin.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the OEM harness from the VSS.
  • Disconnect the OEM harness connector from the ECM.

Action

  • Measure the resistance from pins 3 and 7 to every other pin in the OEM harness connector.
OK NOT OK
More than 100k ohms Repair or replace the OEM harness. Refer to Procedure 019-071.

Guided Step 3 – Check the OEM components.

Guided Step 3A – Check for an external recording device.

Conditions

Turn keyswitch OFF.

Action

Note: Some applications, i.e., automatic transmissions, condition the signal and supply the conditioned signal to pin 7 as a digital vehicle speed signal. This type of signal must not feed pin 3. No splices should exist between the VSS and conditioning circuit to include another device.

Note: The variable reluctance (magnetic pickup) VSS does not source enough power to allow more than one device to exist between the ECM or conditioning circuit and the vehicle speed sensor.
OK NOT OK
No external device Disconnect device from circuit.

Guided Step 3B – Check for a gear slipping on the shaft.

Conditions

  • Turn keyswitch OFF.
  • Remove the VSS.

Action

  • Check to make sure the transmission gear inside the sensor mounting is not slipping on the shaft. Do this by trying to spin the gear with a standard screwdriver.
OK NOT OK
Gear attached properly Repair transmission gear. Refer to the OEM troubleshooting and repair manual.

Guided Step 4 – Check for electrical interference.

Guided Step 4A – Check vehicle speed.

Conditions

  • Connect all components.

Action

  • Check the vehicle speed with these conditions:
  • Turn keyswitch ON, vehicle not running.
  • Cranking engine with starter.
  • Vehicle parked, engine idling, with electronic service tool.
OK NOT OK
No vehicle speed; vehicle parked Vehicle speed registers; vehicle parked.

Guided Step 4B – Check for good vehicle grounding.

Conditions

  • Turn keyswitch OFF.

Action

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

  • Measure within OEM specifications for voltage drop under electrical load.
 Correct vehicle grounds.

Guided Step 4C – Check vehicle speed with the ECM away from the engine block.

Conditions

  • Turn keyswitch OFF.
  • Connect all electrical components.

Action

Monitor vehicle speed with these conditions:

  • Turn keyswitch ON, engine not running.
  • Turn keyswitch ON, engine cranking with starter motor.
  • The engine is idling, vehicle parked, and electronic service tool connected.
OK NOT OK
No vehicle speed on electronic service tool Vehicle speed on electronic service tool.

Guided Step 4D – Check the alternator.

Conditions

  • Remove the alternator belt.
  • Connect the engine harness connector to the ECM.

Action

  • Start engine and let idle.
  • Read vehicle speed with electronic service tool.
OK NOT OK
No vehicle speed on electronic service tool. Vehicle speed registers on electronic service tool.

  • Repair or replace alternator. Note: A capacitor across alternator output (observe proper polarity of capacitor) can help alternator-induced voltage spikes. See OEM manual for specifications.

Guided Step 4E – Check other OEM components for shorting to ground.

Conditions

  • Reconnect all components.
  • Start engine and allow it to idle.

Action

  • Disable or unplug OEM components that possibly will intermittently short to ground, such as fan clutch relays, engine speed sensors in the flywheel, tachographs, engine brakes, OEM relays, vehicle speed sensors, or the alternator.
  • Route alternator power for keyswitch to ECM and isolate OEM keyswitch.
OK NOT OK
No vehicle speed on the electronic service tool Vehicle parked; electronic service tool displays a vehicle speed.

Guided Step 4F – Check engine brake circuit.

Conditions

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

Action

  • Start engine.
OK NOT OK
No vehicle speed on the electronic service tool. Electronic service tool registers vehicle speed while vehicle is parked.

  • Repair or replace engine brake solenoids or engine brake harness.

 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead.
Guided Step 4G – Check datalink wiring for short circuit to ground.

Conditions

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

Action

  • Measure from pin 8 of the OEM connector at the ECM to the engine block ground.
  • Measure from pin 27 of the OEM connector at the ECM to the engine block ground.
  • Measure from pin 10 of the sensor connector at the ECM to the engine block ground.
  • Measure from pin 20 of the sensor connector at the ECM to the engine block ground.
  • Check OEM datalink power for short circuit to ground, also.

Note: After checking for datalink shorts to ground, monitor for vehicle speed, with the vehicle parked, keyswitch ON, engine not running, while starting the engine, and while the engine is idling.
OK NOT OK
More than 100k ohms, vehicle speed on service tool, vehicle parked Service tool shows no vehicle speed, while vehicle is parked, less than 100k ohms.

  • Repair the datalink wiring. Refer to Procedure 019-201, 019-202, or 019-205.
  • Replace engine harness. Refer to Procedure 019-043.
  • Replace the OEM harness. Refer to the OEM manual for procedure.

 CAUTION 

 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead.
Guided Step 4H – Check injector circuits and fuel shutoff solenoids for short circuit to ground.

Conditions

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

Action

  • Check injector circuits for short circuits to ground.
  • Check fuel shutoff solenoid and associated circuits for short circuits to ground.
OK NOT OK
More than 100k ohms and no vehicle speed on the electronic service tool.

  • Repair or replace the component that failed.
 Less than 100k ohms and vehicle parked; electronic service tool registers vehicle speed.

Guided Step 4I – Check for EMI noise or feedback from another device on VSS circuit.

Conditions

  • Disconnect speedometer feed from VSS or any other devices wired to the second coil on the dual-coil VSS. Do not disconnect ECM side of the dual-coil VSS.
  • Disconnect any other devices sharing output signal (signal out of vehicle interface module) with the ECM digital VSS input such as a speedometer, tachograph, etc. Typically, this is a single-coil VSS application used, for instance, in an electronic Allison transmission.
  • Connect all other components.

Action

Monitor vehicle speed during:

  • Turn keyswitch ON, engine not running.
  • Crank engine over with the starter motor.
  • Vehicle parked; engine idling, with an electronic service tool.
OK NOT OK
Vehicle parked; no vehicle speed on service tool.

  • Repair or replace OEM component causing noise on the VSS.
 Vehicle parked; vehicle speed on service tool.

Guided Step 4J – Check for vehicle speed with VSS disconnected.

Conditions

  • Disconnect VSS from the OEM harness.
  • Install electronic service tool.

Action

Monitor vehicle speed with service tool:

  • Turn keyswitch ON, engine not running.
  • Crank engine with starter motor.
  • Vehicle parked; engine idling.

Note: Perform all steps with vehicle parked.
OK NOT OK
Vehicle parked, no vehicle speed.

  • Drivetrain vibration, loose pickup gear, or VSS sensitivity issue. Correct the issue
 Vehicle parked; vehicle speed registered by electronic service tool.

  • Replace OEM wiring with shielded, twisted pair cable and ground one end of the shield to negative (-) battery. Do not ground both ends of the shield. Ground loop noise can be induced into the VSS.

Guided Step 5 – Clear the fault codes.

Guided Step 5A – Disable the fault code.

Conditions

  • Connect all the components.

Action

  • Drive the vehicle. The vehicle speed must exceed 10 mph.
OK NOT OK
Fault Code 241 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 5B – Clear the inactive fault codes.

Conditions

  • Connect all the components.

Action

  • Erase the inactive fault codes using INSITE™.
OK NOT OK
All fault codes cleared Troubleshoot any remaining active fault codes.
Repair complete
Appropriate troubleshooting chart
Last Modified:  29-Oct-2003
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