G3600 A4 Engines Speed/Timing - Test Caterpillar


Speed/Timing - Test
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Use this procedure to troubleshoot a problem with one or more of the engine speed/timing sensors. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

Table 1
J1939 Code and Description  Comments 
190-8
Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period 
The engine speed from this sensor is ignored.
The code is active.
The code is logged if the pattern from the timing ring returns for five seconds. 
723-8
Engine Speed Sensor #2 : Abnormal Frequency, Pulse Width, or Period 
The code is latched in the active state until the power to the Electronic Control Module (ECM) is cycled.
The offset for the timing calibration is set to zero while the diagnostic code is active.
The sensor is ignored. The engine speed is calculated by using only the signal from the primary speed/timing sensor. 
723-19
Engine Speed Sensor #2 : Data Error 
The ECM has been notified by the Integrated Sensing Module (ISM) that the engine speed signal is no longer detected. 

The engine speed/timing sensor provides information about engine speed and about the position of the crankshaft to the Electronic Control Module (ECM). The sensor monitors the rotation of a speed-timing wheel. The passive sensor has a coil around a permanent magnet which generates voltage as the teeth of the speed-timing wheel pass through the magnetic field. The speed-timing wheel is installed on the rear of the right camshaft.

The engine speed/timing sensor generates a signal that matches the pattern of the speed-timing wheel's teeth. The ECM monitors the speed of the signal pulses in order to determine the engine rpm.

The speed-timing wheel has a special tooth pattern that indicates the position of the camshaft. The speed-timing wheel has 36 teeth that are evenly spaced and one extra tooth. The number one cylinder is at the top center position on the compression stroke when the centerline of the first tooth after the extra tooth aligns with the centerline of the sensor. All 37 teeth pass the sensor during one revolution of the camshaft or two revolutions of the crankshaft.

With the information from the engine speed/timing sensor, the ECM is able to calculate the positions of the pistons in the cylinders. The ECM determines the desired ignition timing according to the engine speed and to the load. If detonation is detected in any of the cylinders, the ECM retards the timing of the affected cylinders. The ECM sends voltage pulses to the ignition transformers for firing the spark plugs according to the desired timing.

If the ECM detects a problem with the engine speed/timing sensor's signal, the ECM will shut down the engine. If there is a problem with the engine speed/timing sensor's signal during start-up, the ECM will not initiate the ignition. The engine will not start. The corresponding diagnostic code is generated.

If the engine speed/timing sensor is replaced, the sensor does not require calibration and the speed-timing wheel does not require adjustment.

The most likely causes of the diagnostic code are a poor electrical connection or a problem in a wiring harness. The next likely cause is a problem with the engine speed/timing sensor. The least likely cause is a problem with the ECM.

Logged diagnostic codes provide a historical record. Before you begin this procedure, use Cat® Electronic Technician (ET) to print the logged codes to a file.

The troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.



Illustration 1g03810303

Table 2
Troubleshooting Test Steps  Values  Results 

1. Check for Codes

A. Connect Cat® Electronic Technician (ET) to the service tool connector.

B. Start the engine.

C. Run the engine until normal operating temperature is reached.

Note: If the engine will not start, monitor the engine rpm on Cat ET while the engine is being cranked. If necessary, power Cat ET from another battery while the engine is being cranked.

D. Determine if a code is active or logged.
 

Codes
 

Result: A -8 code is not active or logged.

Repair: Refer to the appropriate engine symptom in this Troubleshooting manual.

Result: A -8 code is active or logged.

Proceed to Test Step 2.

Result: No engine rpm. Cat ET is not reporting engine rpm for at least one engine speed/timing sensor while the engine is cranked.

Proceed to Test Step 3.
 

2. Check the Installation of the Sensor Assembly

A. Turn the main disconnect switch to the OFF position.

B. Visually inspect the sensors without removing the sensor assembly from the engine.

C. Remove the engine speed/timing sensor from the engine.

D. Ensure that the O-ring seals are installed and free of damage.
 

Sensor
 

Result: The O-ring seals are properly installed. The bracket and the seals are free of damage.

Repair: Perform the following procedure:

1. Lubricate the O-ring seals with oil.

2. Fully seat the sensor into the housing.

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

3. Tighten the bolts.

4. Connect the connector.

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

Proceed to Test Step 3.

Result: At least one of the sensor assembly components is NOT OK.

Repair: Install a new sensor assembly.

If the problem is not resolved, proceed to Test Step 3.
 

3. Inspect the Electrical Connectors and the Wiring

A. Turn the main disconnect switch to the OFF position.

B. Thoroughly inspect the connectors. Refer to Troubleshooting, "Electrical Connectors-Inspect" for additional information.

C. Perform a 45 N (10 lb) pull test on the connector wires.

D. Check the harness for abrasions and pinch points.
 

Connectors and Wiring
 

Result: The connectors and wiring appear to be OK.

Proceed to Test Step 4.

Result: There is a problem with the connectors and/or wiring.

Repair: Repair or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled.

If the problem is not resolved, proceed to Test Step 4.
 

4. Check the Supply Voltage to the Sensors

A. Turn the main disconnect switch to the OFF position.

B. Disconnect the connectors for the speed/timing sensors.

C. Restore electrical power to the ECM.

D. Measure the voltage at the sensor connectors between following terminals:

- Terminal A and Terminal B
 

Supply Voltage
 

Result: The battery voltage is OK.

Proceed to Test Step 5.

Result: The battery voltage is NOT OK.

Proceed to Test Step 7.
 

5. Check the Signal Voltage at the Sensor

A. Crank the engine and measure the voltage at the sensor connectors between following:

- Signal wire and Terminal B
 

Signal Voltage
 

Result: The signal voltage is OK. The voltage measures less than 2.5 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.

Proceed to Test Step 6.

Result: The signal voltage is NOT OK.

Repair: Replace the engine speed/timing sensor. A timing calibration is not required when the sensors are replaced.

If the problem is not resolved, proceed to Test Step 6.
 

6. Check the Signal Voltage at the ECM

A. Turn the main disconnect switch to the OFF position.

B. Remove the signal wire from the ECM connector P2-35.

C. Restore electrical power to the ECM.

D. Crank the engine and measure the voltage between the following:

- Primary sensor signal wire and P1-18

E. Turn the main disconnect switch to the OFF position.

F. Remove the signal wire from the ECM connector P2-46.

G. Restore electrical power to the ECM.

H. Crank the engine and measure the voltage between the following:

- Secondary sensor signal wire and P1-5
 

ECM Signal Voltage
 

Result: The signal voltage is OK. 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.

Proceed to Test Step 7.

Result: The signal voltage is not OK. There is a problem between the ECM and the engine speed/timing sensor.

Repair: Repair or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled.

If the problem is not resolved, proceed to Test Step 7.
 

7. Check the Supply Voltage for the Engine Speed/Timing Sensors at the ECM

A. Turn the main disconnect switch to the OFF position.

B. Remove the supply wire from ECM connector P2-29. Install a wire jumper into the socket P2-29.

C. Reconnect ECM connector J2/P2.

D. Restore electrical power to the ECM.

E. Measure the supply voltage between the following:

- P2-5 (ECM connector) and P2-29 (jumper wire)
 

ECM Supply Voltage
 

Result: The supply voltage is OK. There is an open circuit or a short circuit between the ECM and the connectors for the engine speed/timing sensors.

Repair: Repair or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled.

Verify that the repair eliminated the problem.

Result: The supply voltage is not OK. There appears to be a problem with the ECM.

Repair: Replace the ECM. Refer to Troubleshooting, "Test ECM Mode".

Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance.

Verify that the repair eliminated the problem.
 

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).

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