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DTC 51, Switch Condition Signal

ECM receives a signal when the following occurs:

DTC 51 indicates that above systems are functioning normally. If DTC 51 is not indicated with accelerator pedal 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 DTC 51 is indicated without the above conditions, a fault is also present.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Determines if systems are functioning normally in test diagnostic mode.
  2. Checks if TP sensor circuit is operating normally.
  3. Checks for a short to ground in A/C circuit, an open in PNP switch circuit, an 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.
Fig 1: DTC 51 Schematic (Prizm 1.6L VIN 6) Switch Condition Signal
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Fig 2: DTC 51 Diagnostic Flow Chart - 1 Of 2 (Prizm 1.6L VIN 6) Switch Condition Signal
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Fig 3: DTC 51 Diagnostic Flow Chart - 2 Of 2 (Prizm 1.6L VIN 6) Switch Condition Signal
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