C15 and C18 Engines for Caterpillar Built Machines Engine Speed/Timing Sensor Circuit - Test Caterpillar

System Operation Description:

Use this procedure to troubleshoot any suspect problems with the following sensors:

• Primary engine speed/timing sensor

• Secondary engine speed/timing sensor

This procedure covers the following diagnostic codes:

• 190-08 Engine Speed signal abnormal

• 342-08 Secondary Engine Speed signal 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 Electronic Control Module (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 period of 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.

Illustration 1	g01142083
Schematic for speed/timing sensors

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove the electrical power from the ECM.
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   Illustration 2	g01434699
   Left side engine view (typical example) (1) Primary speed/timing sensor connector (2) Secondary speed/timing sensor connector (3) P2 ECM connector

2. Thoroughly inspect connectors (1), (2), and (3). Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.
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   Illustration 3	g01237789
   P2 connector (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 4	g01155187
   Connector for the engine speed/timing sensors (1) Speed/timing sensor (−) (2) Speed/timing sensor (+)

3. 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.

4. Check the allen head screw for each ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

5. 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 completely 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 completely coupled. Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect AVSpare Electronic Technician (ET) to the service tool connector.

2. Restore the electrical power to the ECM.

3. 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.

4. 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.

5. Check for one of the following logged diagnostic codes or active diagnostic codes:

   • 190-08 Engine Speed signal abnormal

   • 342-08 Secondary Engine Speed signal abnormal

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 3.

• 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 3. Check the Installation of the Sensor Assembly

1. Remove the electrical power from the ECM.
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   Illustration 5	g01434702
   Sensor installation (4) Mounting surface (5) Flange (6) Bracket

2. Visually inspect the sensors without removing the sensor assembly from the engine. Flange (5) must be flush against mounting surface (4) in order to ensure proper operation.

   Inspect bracket (6). 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 6	g01434706
   Engine speed/timing sensors (7) Bracket (8) Secondary speed/timing sensor (9) Mounting plate (10) O-ring seals (11) Bracket (12) Primary speed/timing sensor

3. Remove the suspect engine speed/timing sensor from the engine.

4. Ensure that O-ring seals (10) are installed on sensors (8) and (12), and on mounting plate (9). 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 properly install a sensor assembly:

  1. Lubricate the O-ring seals with oil.

  2. Fully seat each sensor into the housing.

     Note: If the sensor assembly will not fully seat into the engine, replace the sensor assembly.

  3. Tighten the bolt for brackets (7) and (11).

  4. Connect the connector and verify that the latch tab of the connector is securely latched.

  5. Ensure that the harness is properly secured, and that the tie-wraps are placed in the correct location.

  Proceed to Test Step 4.

• Not OK - At least one of the sensor assembly's components is not OK.

  Repair: Obtain a new sensor assembly. Perform the following procedure in order to properly install the sensor assembly:

  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.

  1. Lubricate each O-ring with oil.

  2. Fully seat the sensor into the housing.

  3. Tighten the bracket bolt.

  4. Connect the connector and verify that the latch tab of the connector is securely latched.

  5. Ensure that the harness is properly secured, and that the tie-wraps are placed in the correct location.
  Verify that the problem is resolved.

  STOP

Test Step 4. Measure the Sensor Resistance through the Engine Harness

1. Disconnect the P2 connector.

2. Perform the following procedure in order to measure the resistance of the primary engine speed/timing sensor:

   1. Measure the resistance from P2-35 (primary engine speed/timing +) to P2-25 (primary engine speed/timing −).

      Resistance ... 110 to 200 Ohms

3. Perform the following procedure in order to measure the resistance of the secondary engine speed/timing sensor:

   1. Measure the resistance from P2-46 (secondary engine speed/timing +) to P2-47 (secondary engine speed/timing −).

      Resistance ... 1000 to 1200 Ohms

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. Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  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

1. Disconnect the engine harness from the suspect sensor.

2. For the primary engine speed/timing sensor, measure the resistance between J401-2 (primary engine speed/timing +) to J401-1 (primary engine speed/timing −).

   Resistance ... 110 to 200 Ohms

3. For the secondary engine speed/timing sensor, measure the resistance between J402-2 (secondary engine speed/timing +) to J402-1 (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:

  1. Lubricate the O-ring seal of the new sensor with oil.

  2. Fully seat the sensor into the housing.

  3. Tighten the bracket bolt.

  4. Connect the connector and verify that the latch tab of the connector is securely latched.

  5. Ensure that the harness is secured in the proper location. Verify that the problem has been resolved.

  STOP