Use this procedure to troubleshoot the electrical system if a problem is suspected with the engine speed/timing sensor or if a diagnostic code in Table 1 is active.
| 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 engine speed is greater than zero rpm and the pattern from the timing ring is incorrect for five seconds. | The engine speed is set to zero rpm. The code is active. The code is logged if the pattern from the timing ring returns for five seconds. |
| 342-8 Secondary Engine Speed Sensor abnormal frequency, pulse width, or period | ||
The Electronic Control Module (ECM) provides the engine speed/timing sensor with 12 ± 1 VDC. The engine speed/timing sensor provides a pulse signal to the ECM. The signal is created as the timing reference gear rotates past the pickup of the engine speed/timing sensors. The timing reference gear is mounted on the rear of the left camshaft. A unique tooth pattern on the timing reference gear allows the ECM to determine the crankshaft position, rotation, and rpm.
If the primary engine speed/timing sensor fails, the ECM will use the secondary engine speed/timing sensor until electrical power is removed from the ECM. In order to prevent any unnecessary down time, the primary engine speed/timing sensor should be repaired or replaced at the earliest possible convenience.
The engine speed/timing sensor generates a pulse signal to the ECM as each tooth of the timing reference gear passes the sensor. The ECM counts the pulses in order to determine the engine rpm. The ECM memorizes the pattern of the pulses. The ECM compares that pattern to a standard pattern in order to determine the crankshaft position. The ECM uses this information to determine the position of the No. 1 piston. The ECM then triggers each fuel injector to fire in the correct firing order and at the correct time. The actual timing and duration of each injection is determined by the ECM. The ECM uses engine rpm and engine load to determine the timing and duration of injection. The loss of the signal from the engine speed/timing sensor generates a diagnostic code. The loss of the signals from both of the engine speed/timing sensors triggers the termination of the signals to the fuel injectors.
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| Illustration 1 | g01265854 |
Schematic for the engine speed/timing sensors and the timing calibration sensor | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.
- Turn the breaker for the ECM to the OFF position.
- Thoroughly inspect connectors (1). Also, thoroughly inspect the connectors for sensors (2), (3), and (4). Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
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| Illustration 2 | g01228838 |
Location of the J1/P1 ECM connectors (typical front side engine view) (1) J1/P1 ECM connectors | |
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| Illustration 3 | g01215178 |
Location of the engine speed/timing sensors (typical left side engine view) (2) Primary engine speed/timing sensor (3) Secondary engine speed/timing sensor | |
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| Illustration 4 | g01228794 |
Location of the timing calibration probe (typical right side engine view) (4) Timing calibration sensor | |
- Perform a 45 N (10 lb) pull test on each wire in the ECM connector and the sensor connectors that are associated with the circuit.
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| Illustration 5 | g01265855 |
P1 ECM connector (P1-13) Secondary engine speed/timing signal (P1-33) Primary engine speed/timing signal (P1-40) Engine timing calibration − (P1-41) Engine timing calibration + (P1-43) +12 V supply (P1-51) Digital return | |
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| Illustration 6 | g01159881 |
Sensor connector (Terminal A) Sensor supply (Terminal B) Sensor return (Terminal C) Signal | |
- Check the allen head screw at each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque values.
- Check the harness and the wiring for abrasion and for pinch points.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion or of pinch points.
Results:
- OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
- Not OK - There is a problem with the connectors and/or 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 2. Check for "ACTIVE" Diagnostic Codes
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Turn the breaker for the ECM to the ON position.
- Turn the switch that provides power to the keyswitch input for the ECM to the ON position.
- Check the diagnostic codes on Cat ET.
- Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.
- Turn the breaker for the ECM to the OFF position.
Expected Result:
No diagnostic codes are active.
Results:
- OK - The 190-8 diagnostic code or the 342-8 diagnostic code is not active.
Repair: There may be an intermittent problem in the circuit. If an intermittent problem is suspected, refer to Troubleshooting, "Inspecting Electrical Connectors".
STOP
- Not OK - The 190-8 diagnostic code or the 342-8 diagnostic code is active. Proceed to Test Step 3.
Test Step 3. Inspect the Engine Speed/Timing Sensor
- Remove the suspect engine speed/timing sensor.
- Inspect the sensor tip for damage.
Expected Result:
The center of the tip of the engine speed/timing sensor is free of damage.
Results:
- OK - The engine speed/timing sensor is undamaged. Reinstall the sensor. Proceed to Test Step 4.
- Not OK - The engine speed/timing sensor is damaged.
Repair: Replace the engine speed/timing sensor. Calibrate the sensor. Refer to Troubleshooting, "Engine Speed/Timing Sensor - Calibrate".
STOP
Test Step 4. Check the Supply Voltage to the Engine Speed/Timing Sensor
- Disconnect the connector for the suspect engine speed/timing sensor.
- Turn the breaker for the ECM to the ON position.
- Turn the switch that provides power to the keyswitch input for the ECM to the ON position.
- Measure the voltage between terminal A and terminal B at the connector for the suspect engine speed/timing sensor.
Expected Result:
The supply voltage is 12 ± 1 VDC.
Results:
- OK - The supply voltage is 12 ± 1 VDC. The correct supply voltage is reaching the connector for the engine speed/timing sensor. Proceed to Test Step 5.
- Not OK - The supply voltage is not 12 ± 1 VDC. There is a problem in the harness between the ECM and the connector for the engine speed/timing sensor. There may be a problem with the ECM. Proceed to Test Step 7.
Test Step 5. Check the Signal Voltage at the Engine Speed/Timing Sensor
- Turn the breaker for the ECM to the OFF position.
- Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.
- Remove the wire from terminal location C on the sensor side of the suspect sensor connector.
- Reconnect the suspect sensor at the sensor connector.
- Turn the breaker for the ECM to the ON position.
- Turn the switch that provides power to the keyswitch input for the ECM to the ON position.
- Measure the voltage between the suspect sensor signal wire and terminal B of the suspect sensor connector. Also, crank the engine and measure the voltage between the suspect sensor signal wire and terminal B during engine cranking.
- Turn the breaker for the ECM to the OFF position.
- Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.
- Restore the wiring to the original configuration.
Expected Result:
The voltage measures less than 3 VDC or more than 9 VDC when the ECM is powered and the engine is not cranking. While the engine is cranking, the voltage is between 2 VDC and 7 VDC.
Note: The voltage output is determined by the presence or the absence of a tooth on the timing gear.
Results:
- OK - The engine speed/timing sensor is producing the correct output signal voltage. The problem is in the harness between the ECM and the sensor connector. There may be a problem with the ECM. Proceed to Test Step 6.
- Not OK - The engine speed/timing sensor is not producing the correct output signal.
Repair: Replace the engine speed/timing sensor. Calibrate the sensor. Perform the calibration procedure Troubleshooting, "Engine Speed/Timing Sensor - Calibrate".
STOP
Test Step 6. Check the Signal Voltage at the ECM
- Disconnect the J1/P1 ECM connector.
- Remove the signal wire for the suspect sensor from ECM connector P1. Refer to Illustration 1 for the correct wire for the suspect sensor.
- Reconnect the J1/P1 ECM connector.
- Turn the breaker for the ECM to the ON position.
- Turn the switch that provides power to the keyswitch input for the ECM to the ON position.
- Measure the signal voltage between the signal wire and engine ground.
- Crank the engine and measure the signal voltage between the signal wire and engine ground.
- Turn the breaker for the ECM to the OFF position.
- Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.
- Restore the wiring to the original configuration.
Expected Result:
The voltage measures less than 3 VDC or more than 9 VDC when the ECM is powered and the engine is not cranking. While the engine is cranking, the voltage is between 2 VDC and 7 VDC.
Note: The voltage signal is generated by the presence or the absence of a tooth on the timing gear.
Results:
- OK - The correct voltage is measured on the signal wire that was removed from the ECM connector.
Repair: The ECM does not appear to be reading the signal. Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".
STOP
- Not OK - The voltage is incorrect on the signal wire that was removed from the ECM connector.
Repair: The problem is in the harness between the ECM and the engine speed/timing sensor. Repair the connectors and/or wiring or replace the connectors and/or wiring.
STOP
Test Step 7. Check the Supply Voltage for the Engine Speed/Timing Sensor at the ECM
- Turn the breaker for the ECM to the OFF position.
- Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.
- Disconnect the J1/P1 ECM connector.
- Fabricate two jumper wires that are long enough to be used as a test circuit at the ECM connector. Crimp a connector socket to one end of each of the jumper wires.
- Remove the wire from terminal location P1-43 at the ECM connector. Install one of the jumper wires into terminal location P1-43.
- Remove the wire from terminal location P1-51 at the ECM connector. Install the other jumper wire into terminal location P1-51.
- Connect the J1/P1 ECM connector.
- Turn the breaker for the ECM to the ON position.
- Turn the switch that provides power to the keyswitch input for the ECM to the ON position.
- Measure the supply voltage between the jumper wires in terminal locations P1-43 and P1-51.
- Turn the breaker for the ECM to the OFF position.
- Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.
- Restore the wiring to the original configuration.
Expected Result:
The supply voltage is 12 ± 1 VDC.
Results:
- OK - The supply voltage is 12 ± 1 VDC.
Repair: There is a problem in the harness wiring between the ECM and the connector for the engine speed/timing sensor. Repair the connectors and/or wiring or replace the connectors and/or wiring.
STOP
- Not OK - The supply voltage is not 12 ± 1 VDC. The supply voltage is incorrect.
Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".
STOP