Workshop Hints

Workshop Hints

Air Management
Unmetered air leaks can be misleading when diagnosing faults causing "Malfunction Indicator Light"/driveability complaints. Refer to S.I. # 11 03 92 (3500) for testing intake vacuum leaks.

Crankcase Ventilation System
A fault in this system can often "mislead" diagnosis. This type of fault can produce:
- Mixture/misfire defect codes
- Whistling noises
- Performance/driveability complaints
- Crankcase Ventilation System Check S.I> #11 05 98

Throttle Position Sensors - Testing
The Throttle Position Sensors (potentiometers)can be tested with the following methods:







- DISplus Status Page (approx. 0.5v to 4.5v)
- DISplus Oscilloscope - Select from the Preset Measurements which requires taking the measurement with the ECM and Universal Adapter connected to the circuit.
- Resistance check of the entire circuit, using the Universal Adapter with the ECM disconnected.

Idle Air Actuator - Testing







- The Idle Air Actuator and idle air circuit (passage ways) should be checked for physical obstructions.
- The resistance of the valve winding should be checked. The ECM output and Idle Speed Control Valve operation can be tested by "Component Activation" on the DISplus/MoDIC.
- The Pulse Width Modulated ground output from the ECM can be tested using the DISplus/MoDIC Oscilloscope.
- Consult Technical Data for specified idle speed.