Use this procedure to troubleshoot the electrical system if a problem is suspected with the primary engine speed/timing sensor or with the secondary engine speed/timing sensor. Use this procedure to troubleshoot the electrical system if any of the diagnostic codes in Table 1 are active or easily repeated.
| Diagnostic Codes Table | ||
|---|---|---|
| Code and Description | Conditions which Generate this Code | System Response |
| 190-8 Engine Speed Sensor abnormal frequency, pulse width, or period | The signal from the primary engine speed/timing sensor is intermittent or the signal has been lost. | The code is logged. If a valid signal is not received from the primary engine speed/timing sensor, the Electronic Control Module (ECM) will default to the secondary engine speed/timing sensor. The engine will shut down only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are abnormal. |
| 342-8 Secondary Engine Speed Sensor abnormal frequency, pulse width, or period | The signal from the secondary engine speed/timing sensor is intermittent or the signal has been lost. | The code is logged. If a valid signal is not received from the secondary engine speed/timing sensor, the ECM will default to the primary engine speed/timing sensor. The engine will shut down only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are abnormal. |
The engine uses two engine speed/timing sensors. The secondary engine speed/timing sensor monitors the camshaft gear and the primary engine speed/timing sensor monitors the crankshaft gear. Both of the engine speed/timing sensors detect the reference for engine speed and timing from a unique pattern on the respective gear. The ECM counts the time between pulses that is created by the sensor as the gear rotates in order to determine rpm.
Under normal operation, the secondary engine speed/timing sensor is used to determine timing for starting purposes. The secondary engine speed/timing sensor is used to determine when the piston in the No. 1 cylinder is at the top of the compression stroke. When the timing has been established, the primary engine speed/timing sensor is then used to determine engine speed and the signal from the secondary camshaft sensor is ignored.
After locating the No. 1 cylinder, the ECM triggers each injector in the correct firing order and at the correct unit injector timing. The actual timing and duration of each injection is based on engine rpm and load. If the engine is running and the signal from the primary engine speed/timing sensor is lost, a slight change in engine performance will be noticed when the ECM performs the changeover to the secondary engine speed/timing sensor. Loss of the signal from the secondary engine speed/timing sensor during engine operation will not result in any noticeable change in engine performance. However, if the signal from the secondary engine speed/timing sensor is not present during start-up the following conditions may exist:
- The engine may require a slightly longer time to start up.
- The engine may run rough for a few seconds until the ECM determines the proper firing order by using the primary engine speed/timing sensor only.
The engine will start and the engine will run when only one sensor signal is present from either of the sensors. The loss of the signal from both of the sensors during engine operation will result in the termination of injection and the shutting down of the engine by the ECM. The loss of the signal from both of the sensors during start-up will prevent the engine from starting.
Both sensors are magnetic sensors with an integral connector. The two sensors are not interchangeable. Do not switch the positions of the sensor. If the sensors are replaced, a timing calibration is not necessary for the engine.
Note: When the sensors are being installed, complete all of the following tasks:
- Lubricate the O-ring with oil.
- Ensure that the sensor is fully seated into the engine before tightening the bracket bolt.
- Ensure that the connector is properly latched.
- Ensure that the harness is properly secured, and ensure that the tie-wraps are placed in the correct location.
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| Illustration 1 | g01375715 |
Schematic for the speed/timing sensors (single ECM system) | |
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| Illustration 2 | g01375711 |
Schematic for the speed/timing sensors (Two ECM system) | |
Test Step 1. Check for Active Diagnostic Codes
- Remove the electrical power from the ECM.
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Restore the electrical power to the ECM.
- Start the engine and run the engine. The problem may occur when the engine is at any operating temperature. However, the problem is more likely to occur when the engine is at the normal operating temperature.
- If the engine will not start, monitor the engine speed on Cat ET while the engine is being cranked. Cat ET may need to be powered from another battery while the engine is being cranked. This is done so that Cat ET will not reset.
Note: Upon initial cranking, the status for engine speed may indicate that the engine speed signal is abnormal. This message should be replaced with an engine speed once the ECM is able to calculate a speed from the signal.
- Check for one of the following logged diagnostic codes or active diagnostic codes:
- 190-08
- 342-08
- 190-08
Expected Result:
One of the above codes are active or logged.
Results:
- No engine rpm - Engine rpm is not indicated on Cat ET. Proceed to Test Step 2.
- Active or logged code - There is an active diagnostic code or a logged diagnostic code for an engine speed/timing sensor. Proceed to Test Step 4.
- No codes - Neither code is active or logged.
Repair: Refer to the appropriate symptoms in Troubleshooting, "Troubleshooting Without a Diagnostic Code".
STOP
Test Step 2. Check the Installation of the Sensor Assembly
- Remove the electrical power from the ECM.
- Visually inspect the sensors without removing the sensor assembly from the engine. Flange (2) must be flush against mounting surface (1) in order to ensure proper operation.
Inspect bracket (3) . Verify that the bracket securely holds the flange of the sensor flush against the mounting surface.
Verify that the bracket is not bent. If the bracket is bent or if an obstruction is preventing the sensor assembly from being installed correctly, the engine will not start.
Note: The bracket cannot be replaced separately.
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| Illustration 3 | g01194044 |
Sensor installation (1) Mounting surface (2) Flange (3) Bracket | |
- Remove the suspect engine speed/timing sensor from the engine.
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| Illustration 4 | g01142103 |
Engine speed/timing sensors (4) Bracket (5) Secondary speed/timing sensor (6) Mounting plate (7) O-ring seals (8) Bracket (9) Primary speed/timing sensor | |
- Ensure that O-ring seals (7) are installed on sensors (5) and (9) , and on mounting plate (6) . Ensure that the O-ring seals are free of damage.
Expected Result:
All of the O-ring seals are properly installed and free of damage. The bracket is free of damage.
Results:
- OK - The O-ring seals are properly installed. The bracket and the seals are free of damage.
Repair: Perform the following procedure in order to install a sensor assembly:
- Lubricate the O-ring seals with oil.
- Fully seat each sensor into the housing.
Note: If the sensor assembly will not fully seat into the engine, replace the sensor assembly.
- Tighten the bolt for brackets (4) and (8) .
- Connect the connector and verify that the latch tab of the connector is securely latched.
- Ensure that the harness is properly secured, and that the tie-wraps are placed in the correct location.
Proceed to Test Step 3.
- Not OK - At least one of the sensor assembly components is not OK.
Repair: Obtain a new sensor assembly. Perform the following procedure in order to install the sensor assembly:
- Lubricate each O-ring with oil.
Note: Do not switch the positions of the sensors. The sensors are not interchangeable. A timing calibration is not required when the sensors are replaced.
- Fully seat the sensor into the housing.
- Tighten the bracket bolt.
- Connect the connector and verify that the latch tab of the connector is securely latched.
- Ensure that the harness is properly secured, and that the tie-wraps are placed in the correct location.
STOP
Test Step 3. Inspect the Electrical Connectors and the Wiring
- Remove the electrical power from the ECM.
- Thoroughly inspect connectors (10) , (11) , and (12) . Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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| Illustration 5 | g01375783 |
Front engine view (10) Secondary speed/timing sensor (11) Primary speed/timing sensor | |
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| Illustration 6 | g01375821 |
Rear engine view (12) P2 ECM connector | |
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the engine speed/timing sensor.
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| Illustration 7 | g01237789 |
Terminal locations at the P2 ECM connector that are for the engine speed/timing sensors (P2-25) Primary engine speed/timing signal (−) (P2-35) Primary engine speed/timing signal (+) (P2-46) Secondary engine speed/timing signal (+) (P2-47) Secondary engine speed/timing signal (−) | |
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| Illustration 8 | g01155187 |
Connector for the engine speed/timing sensors (Terminal 1) Speed/timing sensor (−) (Terminal 2) Speed/timing sensor (+) | |
- Check the allen head screw for each ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
- Check the harness and wiring for abrasion and for pinch points from the engine speed/timing sensors to the ECM.
Expected Result:
All connectors, pins, and sockets are coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.
Results:
- OK - The harness and the wiring appear to be OK. Proceed to Test Step 2.
- Not OK - There is a problem in the connectors and/or wiring.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals for the connectors are properly in place and ensure that the connectors are coupled. Verify that the repair eliminates the problem.
STOP
Test Step 4. Measure the Sensor Resistance through the Engine Harness
- Remove the electrical power from the ECM.
- Disconnect the P2 connector.
- Perform the following procedure in order to measure the resistance of the primary engine speed/timing sensor:
- Measure the resistance from P2-35 (primary engine speed/timing +) to P2-25 (primary engine speed/timing -).
Resistance ... 110 to 200 Ohms
- Measure the resistance from P2-35 (primary engine speed/timing +) to P2-25 (primary engine speed/timing -).
- Perform the following procedure in order to measure the resistance of the secondary engine speed/timing sensor:
- Measure the resistance from P2-46 (secondary engine speed/timing +) to P2-47 (secondary engine speed/timing -).
Resistance ... 1000 to 1200 Ohms
- Measure the resistance from P2-46 (secondary engine speed/timing +) to P2-47 (secondary engine speed/timing -).
Expected Result:
The resistance measurements are within the specifications.
Results:
- OK - The resistance measurements are within the specifications.
Repair: The sensors and the harness are OK. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "ECM - Replace" for details.
STOP
- Not OK - The readings are not within the specifications. The sensor resistance is not within the acceptable range when the sensor resistance is measured through the engine harness. Proceed to Test Step 5.
Test Step 5. Measure the Resistance of the Sensor
- Disconnect the engine harness from the suspect sensor.
- At the sensor connector for the primary engine speed/timing sensor, measure the resistance between terminal 2 (primary engine speed/timing +) and terminal 1 (primary engine speed/timing -).
Resistance ... 110 to 200 Ohms
- At the sensor connector for the secondary engine speed/timing sensor, measure the resistance between terminal 2 (secondary engine speed/timing +) and terminal 1 (secondary engine speed/timing -).
Resistance ... 1000 to 1200 Ohms
Expected Result:
The resistance measurement for the suspect sensor is within the specification.
Results:
- OK - The resistance measurement for the suspect sensor is within the specification.
Repair: There is a problem with the wiring between the engine speed/timing sensor and the ECM. There may be a problem with a connector. Repair the wiring and/or the connector. Replace parts, if necessary. Twisted pair wiring is required. Any new wiring must have at least one twist per inch. Verify that the problem is resolved.
STOP
- Not OK - The resistance measurement for the suspect sensor is not within the specification.
Repair: There is a problem with the sensor. Replace the sensor assembly.Do not switch the positions of the sensors. The sensors are not interchangeable. A timing calibration is not required when the sensors are replaced. Perform the following procedure in order to replace the sensor assembly:
- Lubricate the O-ring seal of the new sensor with oil.
- Fully seat the sensor into the housing.
- Tighten the bracket bolt.
- Connect the connector and verify that the latch tab of the connector is securely latched.
- Ensure that the harness is secured in the proper location. Verify that the problem has been resolved.
STOP