Use this procedure to troubleshoot the electrical system if a problem is suspected with the engine speed/timing sensor or if one of the diagnostic codes in Table 1 is active.
| Diagnostic Codes Table | ||
|---|---|---|
| Code and Description | Conditions which Generate this Code | System Response |
| 190-2 Engine Speed Sensor erratic, intermittent, or incorrect | The engine speed signal cannot be detected. The timing gear pattern returns within one second before being lost and the battery voltage is greater than 9 VDC for the last two seconds. The code will be active and logged if the Electronic Control Module (ECM) detects an incorrect signal for one second. The battery voltage is greater than 9 VDC for the last two seconds. | The secondary engine speed/timing signal will be used if the primary engine speed/timing signal is lost. The code is logged. |
| 190-3 Engine Speed Sensor voltage above normal | A wire on the engine speed/timing sensor is disconnected and/or broken. There is a short circuit to the +Battery terminal. | The secondary engine speed/timing signal will be used if the primary engine speed/timing signal is lost. The code is logged. |
The ECM provides the engine speed/timing sensors with a regulated voltage of 12.5 ± 1 VDC. The engine speed/timing sensors provide 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.
The engine speed/timing sensors generate a pulse signal to the ECM as each tooth passes the sensors. 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 cylinder. The ECM then triggers each unit 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 a signal from an engine speed/timing sensor generates a diagnostic on Caterpillar Electronic Technician (ET). If the signals from both the primary engine speed/timing sensor and the secondary engine speed/timing sensor are lost, the ECM will terminate fuel injection.
Note: The generator set may need a jumper wire on the ECS to provide power to the generator control when the main disconnect switch is closed and the ECS is in the OFF/RESET position. Unless a timer is installed in the circuit, this jumper wire also provides power to the keyswitch input of the engine ECM when the battery disconnect switch is closed and the ECS is in the OFF/RESET position. The timer interrupts power to the keyswitch input of the engine ECM when the battery disconnect switch is closed and the ECS is in the OFF/RESET position. Cycling power to the keyswitch input of the ECM will reset the ECM and all active diagnostic codes. The bottom dial on the timer should be set to 0.7. The middle dial on the timer should be set to 3 seconds. The top dial on the timer should be set to E.
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| Illustration 1 | g01341116 |
Typical schematic | |
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| Illustration 2 | g01444508 |
Location of the ECM connectors (1) J2/P2 ECM connectors (2) J1/P1 ECM connectors | |
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| Illustration 3 | g01328997 |
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) +12.5 V supply (P1-51) Digital return | |
Note: The timing calibration sensor is only on the J1/P1 connector for the primary ECM.
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Thoroughly inspect the ECM connector J1/P1. Inspect all of the other connectors for the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
- Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- 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 and 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 an "ACTIVE" or "LOGGED"Diagnostic Code
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Turn the ECS to the STOP mode. Turn the main disconnect switch to the ON position.
- Check the diagnostic codes on Cat ET.
Expected Result:
No diagnostic codes are active or logged repeatedly.
Results:
- OK - A diagnostic code for the engine speed/timing sensor is not active or logged repeatedly.
Repair: The problem is no longer present. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- Not OK - A diagnostic code for an engine speed/timing sensor is active or logged repeatedly. Proceed to Test Step 3.
Test Step 3. Check the Supply Voltage to the Sensors
- Disconnect the connectors for the engine speed/timing sensors.
- Turn the ECS to the STOP mode. Turn the main disconnect switch to the ON position.
- Measure the voltage between terminal A and terminal B at the sensor connectors.
Expected Result:
The supply voltage is 12.5 ± 1 VDC.
Results:
- OK - The supply voltage is 12.5 ± 1 VDC. Proceed to Test Step 4.
- Not OK - The supply voltage is not 12.5 ± 1 VDC. Proceed to Test Step 6.
Test Step 4. Check the Signal Voltage at the Sensor
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Remove the wire from terminal C of the sensor connector.
- Turn the ECS to the STOP mode. Turn the main disconnect switch to the ON position.
- Measure the voltage between the sensor's signal wire and terminal B of the sensor connector. Crank the engine and measure the voltage between the sensor signal wire and terminal B.
- Remove electrical power from the ECM.
- Reconnect the signal wire.
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. Proceed to Test Step 5.
- 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, "Timing - Calibrate".
STOP
Test Step 5. Check the Signal Voltage at the ECM
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Check the signal voltage for the primary engine speed/timing sensor.
- Remove the signal wire 999 from the ECM connector P1-33.
- Reconnect ECM connector J1/P1.
- Restore electrical power to the ECM.
- Measure the voltage between the sensor's signal wire and the digital return on P1-51. Crank the engine and measure the voltage between the sensor signal wire and P1-51.
- Check the signal voltage for the secondary engine speed/timing sensor.
- Remove the signal wire F732 from the ECM connector P1-13.
- Reconnect ECM connector J1/P1.
- Turn the ECS to the STOP mode. Turn the main disconnect switch to the ON position.
- Measure the voltage between the sensor's signal wire and the digital return on P1-51. Crank the engine and measure the voltage between the sensor signal wire and P1-51.
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Replace all wires. Reconnect ECM connector J1/P1.
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 appears at ECM connector P1 but the ECM is not reading the signal.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".
STOP
- Not OK - There is a problem in the engine speed/timing circuit.
Repair: The problem is 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 6. Check the Supply Voltage for the Engine Speed/Timing Sensors at the ECM
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Disconnect ECM connector J1/P1.
- Remove the supply wire 996 from ECM connector P1-43. Install a wire jumper into the socket P1-43.
- Reconnect ECM connector J1/P1.
- Turn the ECS to the STOP mode. Turn the main disconnect switch to the ON position.
- Measure the supply voltage between wire A998 in ECM connector P1-51 and the wire jumper in P1-43.
- Turn the ECS to the OFF/RESET mode. Turn the main disconnect switch to the OFF position.
- Remove the wire jumper and replace all wires. Reconnect ECM connector J1/P1.
Expected Result:
The supply voltage is 12.5 ± 1 VDC.
Results:
- OK - The supply voltage is 12.5 ± 1 VDC. There is an open circuit or a short circuit between the ECM and the connectors for the engine speed/timing sensors.
Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring.
STOP
- Not OK - The supply voltage is not 12.5 ± 1 VDC. The supply voltage is incorrect.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".
STOP