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Home >> Toyota >> 1995 >> Corolla LE >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 1.8L >> Diagnostic Testing >> Code 51 - Switch Condition Signal Circuit >> Diagnosis & Repair
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Diagnosis & Repair

  1. Ensure ignition is off. Connect jumper wire between DLC1 terminals TE2 and E1. Turn ignition on. With transmission in "P" or "N", code output should be normal.
  2. Shift transmission to "R", "D", "2" or "L", Code 51 should be output. Place transmission in Park. Depress accelerator pedal. Code 51 should be output. Release pedal. Code output should be normal. Turn on A/C. Code 51 should be output. Turn off A/C. Code output should be normal.
  3. If PNP switch is suspect, see test procedures in the SYSTEM/COMPONENT TESTS - 1.8L article. Replace as needed. If IDL switch is suspect, go to next step. If A/C switch is suspect, go to step 6). If all components operate correctly, check all connections, problem may be intermittent.
  4. Disconnect TPS harness connector. Measure resistance between terminals IDL and E2. See Figure. Resistance should be less than 2.3 k/ohms with throttle fully closed and infinite resistance with throttle fully open (WOT).
  5. If resistance measured is within specs, inspect circuit between TPS and ECM. Repair as needed. If resistance is NOT within specs, check TPS adjustment. See the SYSTEM/COMPONENT TESTS - 1.8L article. Adjust as necessary. If adjustment is okay, replace TPS.
  6. Disconnect A/C amplifier harness connector (10-pin). A/C amplifier is located behind glove box. Turn ignition on. Measure voltage between A/C amplifier harness connector terminal AC1 (Red/Yellow wire) and ground. If voltage is 9-14 volts, replace A/C amplifier.
  7. If voltage is NOT 9-14 volts, inspect circuits between A/C amplifier and ECM for opens or shorts. If circuits are okay, replace ECM and retest.
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