EXTENSION GP-FAN 3298398 - Caterpillar

Illustration 12 g00754013
Symbol for a diode
Measure the primary circuit by checking the voltage of the blocking diode. Set the multimeter to the diode scale. Connect the multimeter leads to the terminals (A) and (B) of the transformer's connector. The polarity of the leads is not important. Measure the voltage between the terminals. Record the measurement.
Reverse the polarity of the probes and measure the voltage between terminals (A) and (B) again. Record the measurement.Note: The resistance of the secondary coil will vary with the temperature. Illustration 13 demonstrates the relationship between the secondary coil's resistance and the temperature. A reading that is within 1000 Ohms is acceptable. For example, if the transformer's temperature is 60 °C (140 °F), the correct resistance is 22,000 1000 ohms.
Illustration 13 g00863850
Resistance versus temperature (Y) Resistance in ohms (X) Temperature in degrees Celsius (degrees Fahrenheit)
Measure the resistance of the secondary circuit. Set the multimeter to the 40,000 ohm scale. Measure the resistance between mounting flange (1) and terminal (2) for the spark plug's extension.Expected Result:For the primary circuit, one of the voltage measurements is approximately 0.450 VDC. The other voltage measurement is an open circuit.For the secondary circuit, the resistance between the mounting flange and the terminal for the spark plug's extension is within the acceptable tolerance. Results:
Not OK - At least one of the measurements is incorrect. There is a problem with the transformer.Repair: Replace the transformer.STOP
OK - Both of the measurements are correct.Repair: Perform the following steps:
Switch the suspect transformer with a transformer from a different cylinder that is known to be good. Install the transformers.
Reset the control system. Clear any logged codes.
Restart the engine. Operate the engine. Check for a recurrence of the problem.If the problem stays with the suspect transformer, replace the transformer.If the problem stays with the suspect cylinder, continue to troubleshoot the problem according to the type of original diagnostic code. If the original diagnostic code is a "-5 open circuit", proceed to Test Step 4. If the original diagnostic code is a "-6 short", proceed to Test Step 5.Test Step 4. Check the Ignition Harness for an Open Circuit
Turn the engine control switch to the OFF/RESET position. Switch the 16 amp circuit breaker for the ECM OFF.
Illustration 14 g00861936
Typical harness connectors for the transformers
Disconnect the suspect ignition harness from the transformer. Inspect the connectors of the harness and of the transformer for damage and/or for corrosion.
Illustration 15 g00861968
Harness connector for the ignition transformer (A) Transformer's circuit driver (B) Transformer's return (C) Unused
Install a jumper wire with the appropriate connectors onto terminals (A) and (B) of the connector for the suspect ignition transformer.
Remove the P2 connector from the ECM. Identify the correct terminals for the suspect