3176C and 3196 Engines for Caterpillar Built Machines Engine Speed/Timing Sensor Circuit - Test Caterpillar

System Operation Description:

Use this procedure to troubleshoot the system only under the following conditions:

• There is an active diagnostic code or an easily repeated diagnostic code that is associated with the engine speed/timing sensors.

• You have been referred to this test from Troubleshooting, "Troubleshooting without a Diagnostic Code".

The engine uses two engine speed/timing sensors. The secondary engine speed/timing sensor picks up the camshaft gear and the primary engine speed/timing sensor picks up 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 camshaft position sensor is used to determine timing for starting purposes. The camshaft position 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 crankshaft position sensor is then used to determine engine speed and the signal from the 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 crankshaft position sensor is lost, a slight change in engine performance will be noticed when the ECM performs the changeover to the camshaft position sensor. Loss of the signal from the camshaft position sensor during engine operation will not result in any noticeable change in engine performance. However, if the signal from the camshaft position 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 crankshaft position 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 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	g00985645

Note: Do not attempt to disconnect the pigtail from the sensor. The pigtail is sealed in the connector.

Illustration 2	g03343255
P2 ECM connector

Test Step 1. Check for Diagnostic Codes

1. Connect the electronic service tool to the service tool connector.

2. Turn the keyswitch to the ON position.

3. Verify whether any of the following diagnostic codes are active or logged:
   • 190-02 Loss of Engine Speed signal

   • 190-11 Engine Speed Sensor mechanical failure

   • 342-02 Loss of Secondary Engine Speed signal

   • 342-11 Secondary Engine Speed Sensor mechanical failure

4. If the diagnostic code is logged but not active, run the engine until the engine is at normal operating temperature. The problem may only occur when the engine is at the normal operating temperature.

5. If the engine will not start, monitor the engine speed on the electronic service tool while the engine is being cranked. The electronic service tool may need to be powered from another battery while the engine is being cranked in order to ensure that the electronic service tool does not reset.

   Note: Upon initial cranking, the status for engine speed may indicate that the engine speed signal is abnormal. This message will be replaced with an engine speed once the ECM is able to calculate a speed from the signal.

Expected Result:

One or more of the diagnostic codes that are listed above are logged or active.

Results:

• Diagnostic Codes - There is a logged diagnostic code or an active diagnostic code for the engine speed/timing sensors. Proceed to Test Step 3.

• No Diagnostic Codes - There are no diagnostic codes for the engine speed/timing sensors, but the engine is not running properly.

  Repair: Proceed to the appropriate topic in Troubleshooting, "Troubleshooting without a Diagnostic Code".

  STOP

• No Engine rpm - Engine rpm is not indicated on the electronic service tool. Proceed to Test Step 2.

Test Step 2. Check the Installation of the Sensors and the Brackets

Illustration 3	g00810795
Sensors and mounting brackets (typical example)

1. The flange of the sensor should be flush against the engine in order to ensure proper operation.

2. Inspect the bracket in order to ensure that the installation allows the flange of the sensor to be flush against the engine.

   Verify that the bracket is not bent.

   Note: The bracket cannot be replaced separately.

3. Ensure that the O-ring has been installed on the sensor, and ensure that the O-ring is free of damage.

4. If either of the following diagnostic codes is active, there may be a problem with the assembly of the engine:
   • 190-11 Engine Speed Sensor mechanical failure

   • 342-11 Secondary Engine Speed Sensor mechanical failure

Expected Result:

The sensors and the bracket are properly installed.

Results:

• OK - The sensors and the bracket are properly installed. Proceed to Test Step 3.

• Not OK -

  Repair: Perform the following procedure in order to properly install the sensors and the bracket:

  1. Loosen the bolt that holds the sensor mounting bracket to the engine.

  2. Seat the sensor and tighten the bolt.

     If the sensor will not seat, repair the sensor or replace the sensor, as required.

     Note: The sensor must not be removed from the bracket.

  3. Ensure that the sensor is properly oriented and that the harness is secured in the proper location.

  4. Verify that the repair eliminates the problem.

  STOP

Test Step 3. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF position.

2. Thoroughly inspect the J2/P2 ECM connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on the following wires in the P2 ECM connector that are associated with the engine speed/timing sensors:
   • P2:48 (Primary Engine Speed/Timing +)

   • P2:49 (Primary Engine Speed/Timing -)

   • P2:58 (Secondary Engine Speed/Timing +)

   • P2:59 (Secondary Engine Speed/Timing -)

4. Ensure that the latch tab on the connector is properly latched and ensure that the latch tab is fully latched.

5. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

6. Ensure that the harness wiring is not pulled too tightly. When the harness wiring is pulled too tightly, vibrations or movement can cause intermittent connections.

7. Inspect the harness wiring for nicks and abrasions.

8. Ensure that the wiring harness is correctly routed and secured at the proper locations.

Expected Result:

All connectors, pins, and sockets should be completely coupled and/or inserted. The harness and wiring should be free of corrosion, abrasion, and pinch points.

Results:

• OK - The connectors and the wiring are OK. Proceed to Test Step 4.

• Not OK - There is a problem with the connectors and/or the wiring.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 4. Measure the Circuit Resistance at the ECM Connector

1. Disconnect the J2/P2 ECM connector.

2. Use the following procedure to measure the circuit resistance for the crankshaft position sensor:

   1. Measure the resistance between P2:48 (Primary Engine Speed/Timing +) and P2:49 (Primary Engine Speed/Timing -).

      Note: Check for an intermittent problem (open or short) by moving the harness while you measure the resistance. Pull the wires that are directly behind the sensors and shake the wires that are directly behind the sensors.

      Resistance ... 75.0 to 230.0 Ohms

3. Use the following procedure to measure the circuit resistance for the camshaft position sensor:

   1. Measure the resistance between P2:58 (Secondary Engine Speed/Timing +) and P2:59 (Secondary Engine Speed/Timing -).

      Note: Check for an intermittent problem (open or short) by moving the harness while you measure the resistance. Pull the wires that are directly behind the sensors and shake the wires that are directly behind the sensors.

      Resistance ... 600 to 1800 Ohms

Expected Result:

The readings agree with the values that are listed above.

Results:

• OK - Neither a short circuit nor an open circuit is indicated. Proceed to Test Step 6.

• Not OK - The resistance is not within the acceptable range when the circuit resistance is measured through the engine harness. Proceed to Test Step 5.

Test Step 5. Measure the Resistance of the Sensor

1. Turn the keyswitch to the OFF position.

2. Check the harness and the wiring for abrasion and pinch points from the sensor back to the ECM.

3. Disconnect the suspect sensor from the engine harness.

4. Thoroughly inspect the J401/P401 primary engine speed/timing sensor (crankshaft position) connector and the J402/P402 secondary engine speed/timing sensor (camshaft position) connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

5. Use the following procedure to measure the resistance of the crankshaft position sensor:

   1. Disconnect the J401/P401 primary engine speed/timing sensor (crankshaft position) connector.

   2. Measure the resistance between terminal 1 and terminal 2 of the sensor.

      Resistance ... 75.0 to 230.0 Ohms

6. Use the following procedure to measure the resistance of the camshaft position sensor:

   1. Disconnect the J402/P402 secondary engine speed/timing sensor (camshaft position) connector.

   2. Measure the resistance between terminal 1 and terminal 2 of the sensor.

      Resistance ... 600 to 1800 Ohms

Expected Result:

The readings agree with the values that are listed above.

Results:

• OK - The sensor resistance is within tolerance. Proceed to Test Step 6.

• Not OK - The sensor resistance is out of the specified range.

  Repair: Perform the following procedure in order to check and install the new sensor:

  Note: Timing calibration is not necessary following replacement of either of the speed/timing sensors. Refer to the information in the System Operation Section regarding the installation of sensors.

  1. Before installing the new sensor, measure the resistance of the new sensor.

     If the new sensor resistance is in the correct range, install the new sensor in the engine, as follows:

     1. Loosen the bolt that holds the sensor mounting bracket to the engine.

     2. Ensure that the O-ring is installed and free of damage.

     3. Seat the sensor and tighten the bolt.

        If the sensor will not seat, repair the sensor or replace the sensor, as required.

        Note: The sensor must not be removed from the bracket.

     4. Ensure that the sensor is properly oriented and that the harness is secured in the proper location.

  2. Verify that the repair eliminates the problem.

  STOP

Test Step 6. Install a Bypass Harness for the Engine Speed/Timing Sensors

1. Turn the keyswitch to the OFF position.

2. Use the following procedure to bypass the circuit for the crankshaft position sensor:

   1. Remove the E964-WH wire from P2:48 (Primary Engine Speed/Timing +).

   2. Remove the E963-BK wire from P2:49 (Primary Engine Speed/Timing -).

   3. Install a 16 AWG wire with Deutsch sockets on both ends between P2:48 (Primary Engine Speed/Timing +) and P401:2.

   4. Install a 16 AWG wire with Deutsch sockets on both ends between P2:49 (Primary Engine Speed/Timing -) and P401:1.

      Note: Twisted pair wiring is required. Ensure that the wires have at least one twist per inch.

3. Use the following procedure to bypass the circuit for the camshaft position sensor:

   1. Remove the E966-YL from P2:58 (Secondary Engine Speed/Timing +).

   2. Remove the E965-BU from P2:59 (Secondary Engine Speed/Timing -).

   3. Install a 16 AWG wire with Deutsch sockets on both ends between P2:58 (Secondary Engine Speed/Timing +) and P402:2.

   4. Install a 16 AWG wire with Deutsch sockets on both ends between P2:59 (Secondary Engine Speed/Timing -) and P401:1.

      Note: Twisted pair wiring is required. Ensure that the wires have at least one twist per inch.

4. Reconnect the J2/P2 engine harness connector .

5. Start the engine in order to determine if the bypass harness repairs the problem.

6. Turn the keyswitch to the OFF/RESET position.

Expected Result:

The problem is corrected with the installation of the bypass harness.

Results:

• OK - The bypass harness eliminated the problem.

  Repair: Permanently install a new section of harness.

  STOP

• Not OK - The problem remains with the bypass installed.

  Repair: Verify that the correct terminals have been installed in the correct location in the P2 ECM connector. If the temporary harness was installed correctly, install the original wiring.

  Proceed to Test Step 7.

Test Step 7. Check the ECM

1. Turn the keyswitch to the OFF position.

2. Temporarily connect a test ECM.

3. Start the engine. Run the engine in order to repeat the conditions when the problem occurs.

4. If the problem is resolved with the test ECM, reconnect the suspect ECM.

5. If the problem returns with the suspect ECM, replace the ECM.

Verify that the repair eliminates the problem.

Expected Result:

The problem remains with the suspect ECM.

Results:

• OK - The problem is resolved with the test ECM and the problem returns with the suspect ECM.

  Repair: Replace the ECM.Verify that the repair eliminates the problem.

  STOP

• Not OK - The test ECM did not eliminate the problem.

  Repair: Replace the sensor.Verify that the repair eliminates the problem.

  STOP