DTC P1464 DETECTION CONDITION AND POSSIBLE CAUSE

DTC P1464	A/C CONTROL SIGNAL (ACCS) MALFUNCTION
DETECTION CONDITION	P1464 indicates that the ACCS input to the PCM was high during the Self Test.
POSSIBLE CAUSE	A/C was on during Self Test. A/C clutch PWR circuit short to power. Short to power on ACCS circuit. Damaged A/C Demand switch. Damaged A/C clutch relay. Damaged PCM.
HINT	ACCS Description When the A/C cycling switch opens, the PCM will turn off the A/C clutch. The A/C cycling switch circuit to the PCM provides a voltage signal which indicates when the A/C is requested. When the A/C demand switch is turned on, and both the A/C cycling switch and the high pressure contacts of the A/C high pressure switch are closed, voltage is supplied to the ACCS circuit at the PCM. If the ACCS signal is not received by the PCM, the PCM will not allow the A/C to operate.
Courtesy of MAZDA MOTORS CORP.

DTC P1464 INSPECTION

STEP	INSPECTION		ACTION
1	Was PCM Quick Test performed?	Yes	Go to next step.
1	Was PCM Quick Test performed?	No	Perform PCM Quick Test.
2	DTC P1464: CHECK ACCS PID NOTE: Verify that A/C and defrost were OFF during Self Test. If A/C or defrost were on, turn off and rerun Self Test. Key ON, Engine OFF (KOEO). A/C and defrost off. Access ACCS PID. Is ACCS PID on?	Yes	Go to next step.
2		No	The ACCS PID indicates that the ACCS input to the PCM is low. Verify test results. With A/C and defrost OFF, rerun Self Test where P1464 was received. Go to step 7.
3	ACCS PID ON: DISCONNECT A/C CYCLING SWITCH AND CHECK IF ACCS PID TURNS OFF Key OFF. Disconnect A/C Cycling Switch. Key ON, Engine OFF (KOEO). Access ACCS PID. Is ACCS PID off?	Yes	Verify operation of A/C Demand Switch. See 07-01 TROUBLESHOOTING INDEX. If OK, repair short to power in A/C Demand circuit to A/C Cycling Switch. Go to step 7.
3		No	Go to next step.
4	CHECK POWER TO A/C CLUTCH CIRCUIT FOR SHORT TO POWER Key OFF. Disconnect A/C clutch relay. Key ON, Engine OFF (KOEO). Measure voltage between A/C clutch power circuit in harness connector and chassis ground. Key OFF. Was voltage less than 1.0 V?	Yes	Go to next step.
4		No	Repair circuit short to power. Go to step 7.
5	CHECK ACCS CIRCUIT FOR SHORT TO POWER Disconnect PCM. Install Breakout Box, leave PCM disconnected. Key ON, Engine OFF (KOEO). Measure voltage between PCM test pin 41 (ACCS) and PCM test pin 103 (PWR GND). Key OFF. Was voltage less than 1.0 V?	Yes	Go to next step.
5		No	Repair ACCS circuit to power. Go to step 7.
6	CHECK ACCS CIRCUIT VOLTAGE TO PCM WITH A/C CLUTCH RELAY CONNECTED Reconnect A/C clutch relay. Key ON, Engine OFF (KOEO). Measure voltage between PCM test pin 41 (ACCS) and PCM test pin 103 (PWR GND). Key OFF. Was voltage less than 1.0 V?	Yes	Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Go to step 7.
6		No	Replace A/C clutch relay. Go to step 7.
7	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Make sure to reconnect all disconnected connectors. Clear DTCs from PCM memory using NGS tester generic OBD-II function. Perform PCM Quick Test. Is same DTC present?	Yes	Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Repeat PCM QUICK TEST .
7		No	If any other DTC is present, go to applicable DTC inspection. If no DTC is present, troubleshooting complete.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

A/C Control Signal (ACCS) Malfunction

Use the Manual With the Right Hardware

When to See a Mechanic

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