Code 51 (PRIZM) - Switch Condition Signal

ECM receives a signal when the following occurs:

• Accelerator pedal is depressed (indicating throttle lever is in off idle position).
• Vehicle is equipped with A/C and A/C switch is depressed with blower speed selector in any position except OFF (indicating A/C operation has been requested).
• Vehicle is equipped with A/T and selector lever is in Reverse or any forward gear (indicating transaxle is in gear other than Park or Neutral).

Code 51 indicates that above systems are functioning normally. If Code 51 is not indicated with accelerator depressed, A/C is on or with gear selector lever in Reverse or any forward gear (excluding Park or Neutral) with Data Link Connector (DLC) terminals TE2 and TE1 jumpered to ground, a fault is present. If Code 51 is indicated without the above conditions, a fault is also present.

1. Determines if systems are functioning normally in test diagnostic mode.
2. Checks if TP sensor circuit is operating normally.
3. Checks for short to ground in A/C circuit, open in PNP switch circuit, open in TP sensor circuit, or a faulty ECM or A/C amplifier.
4. Checks for short to ground in TP sensor circuit, or a faulty TP sensor or ECM.
5. Checks for short to ground in PNP switch circuit.
6. Determines whether system is functioning normally or if there is a problem in A/C circuit.
7. Determines if A/C amplifier or ECM is faulty.