Diagnostic Aids

For any test that requires probing ECM or component harness connectors, use Connector Test Adapter Kit (J-35616-A). This will prevent damage to harness connector terminals. Check for the following conditions:

Check for skewed or stuck TP sensor. A faulty TP sensor or TP sensor circuit can cause ECM to incorrectly calculate predicted mass airflow value. Observe throttle angle with throttle closed. If throttle angle reading is not within typical scan tool values, check for the following conditions:

Check for sticking throttle plate or excessive deposits on throttle plate or throttle bore, TP sensor signal circuit for short to voltage or for poor connection or high resistance in TP sensor ground circuit.

Check for poor connections at ECM or at component. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connection.

Check for misrouted wiring harness. Inspect harness to ensure that it is not routed too close to high voltage wires (spark plug wires) or too close to high current devices (generator, motors, solenoids).

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at a component, and there is no problem with wiring harness or connections, component may be faulty.

Check for plugged intake air duct or dirty air filter. A wide open throttle acceleration from a stop should cause mass airflow displayed on scan tool to increase from about 4-7 gm/s at idle to 100 gm/s or more at the time of 1-2 shift. If increase is not as specified, check for a restriction.

Check for water entering air intake system and contaminating MAF sensor. Water rapidly cools hot wires in sensor, causing a false indication of excessive airflow. Check air filter housing for evidence of water.