Diagnostic Aids

Checking malfunction history on scan tester may help determine cause of intermittent code. Check tightness of all terminals and connectors.

When attempting to diagnose an intermittent problem, use scan tester to review supplemental diagnostic information. Supplemental data (scan tester MALF HISTORY) can be used to help duplicate an intermittent problem. Using Diagnostic Service Probe (12092782) allows voltage to be read on wires without disconnecting connectors. Normal TP sensor scan voltage should vary smoothly from 0.4 volt to 4.5-4.9 volts as throttle is moved from closed to wide open throttle.

Fig 1: Code 21 Schematic Throttle Position Sensor Signal Voltage High

Fig 2: Code 21 Diagnostic Flow Chart Throttle Position Sensor Signal Voltage High