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DTC P1458: A/C Compressor Control Signal Malfunction: Procedure

  1. Turn ignition on. Set A/C switch off and blower switch to No. 1 position. Backprobe and measure voltage between ECM connector terminal No. 64 (Gray/Red wire) and ground. See Figure. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, check for short to ground or short to power in wire between A/C switch terminal No. 2 (Green/Orange wire) and ECM terminal No. 64 (Gray/Red wire). See Figure. Also, check A/C switch for internal short. If problem exists, repair as necessary.
  2. Turn A/C switch on. Backprobe and measure voltage between ECM connector terminal No. 64 (Gray/Red wire) and ground. If voltage does not exist, go to next step. If voltage exists, repair open in wire(s) or connector(s) between grounding junction connector No. 20 and ECM connector terminal No. 64. Grounding junction connector No. 20 is located behind right side of instrument panel.
    NOTE: A/C switch input circuit starts as Black/Red wire from A/C thermostat, then becomes Brown/Green wire at White 13-pin intermediate connector C225, located behind right side of instrument panel, near kick panel. Brown/Green wire passes through engine compartment fuse/relay box and connects to differential pressure switch, located in right side of engine compartment. Brown/Yellow wire leaves differential pressure switch, passes through engine compartment fuse/relay box and terminates at ECM connector terminal No. 65.
  3. Turn A/C switch and blower switch off. Leave ignition on. Backprobe and measure voltage between ECM connector terminal No. 65 (Brown/Yellow wire) and ground. If voltage is about 5 volts, check for intermittent short between A/C thermostat connector terminal No. 2 (Black/Red wire) and ECM connector terminal No. 65 (Brown/Yellow wire). If problem exists, repair as necessary. If voltage is 8-9 volts, verify A/C switch is off. If A/C switch is on, turn A/C switch off and repeat step 3)  . If A/C switch is off, replace A/C switch. If voltage is about zero volts, check for shorted A/C thermostat. If problem exists, replace A/C thermostat. If problem does not exist, repair short to ground in wire between A/C thermostat and ECM connector terminal No. 65.
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