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DTC codes / Ford codes / P1464

P1464 · FordACCS to PCM High During Self-Test

P1464 on Ford vehicles means the Air Conditioning Clutch Control Switch (ACCS) circuit is reading high voltage at the Powertrain Control Module (PCM) during the self-test. The PCM expects a specific voltage on the ACCS input when it commands the self-test, but instead it sees a voltage above the normal threshold, indicating an open circuit, a faulty switch, or a wiring problem.

SystemPowertrain
Code typeFord specific
SeverityLow
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Often no symptoms besides the warning light, because the self-test failure may not affect normal A/C operation immediately.
  • Air conditioning clutch may not engage, resulting in no cold air from the vents.
  • A/C compressor may run continuously or not at all, depending on the failure mode.
  • Intermittent A/C operation, especially over bumps or in wet conditions, due to a loose connection.
  • Possible slight drop in engine idle quality if the PCM misinterprets the ACCS signal and adjusts idle strategy.
  • No other drivability symptoms are typical unless the fault is accompanied by other codes.

Common causes, most likely first

  1. Open circuit in the ACCS signal wire between the switch and the PCM, often due to a broken wire or corroded connector.
  2. Faulty ACCS switch itself, stuck open or internally damaged.
  3. Poor electrical connection at the ACCS switch or PCM connector, such as loose pins or corrosion.
  4. Damaged or shorted wiring harness, especially where it rubs against engine components or passes through the firewall.
  5. PCM internal fault, though rare, can cause incorrect voltage readings on the ACCS circuit.
  6. Aftermarket accessories or poor previous repairs tapping into the ACCS circuit and altering its voltage.
  7. Extreme temperatures or moisture intrusion into the switch or connector causing high resistance.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in the A/C and PCM systems before proceeding.
  2. Inspect the ACCS switch and its connector for corrosion, loose pins, or physical damage; clean or repair as needed.
  3. Disconnect the ACCS switch and measure resistance across its terminals; compare to Ford specifications, and replace the switch if out of range.
  4. Check the ACCS signal wire from the switch to the PCM for continuity and shorts to voltage or ground; repair any wiring faults.
  5. Measure voltage on the ACCS circuit at the PCM during a self-test or with the key on, engine off, to confirm the high signal; backprobe carefully to avoid damage.
  6. If all wiring and the switch test good, substitute a known-good PCM or perform a PCM reset and retest to rule out an internal PCM fault.
  7. Clear the code and perform a road test with the A/C on to confirm the repair and ensure the code does not return.

ACCS circuit quirks on Ford vehicles

  • A common oversight is assuming the ACCS switch is the same as the A/C pressure switch; on many Fords they are separate, and testing the wrong component wastes time.
  • The ACCS circuit often shares a ground with other sensors, so a bad ground can cause a high voltage reading on the ACCS line even if the switch and wiring are fine.
  • P1464 can be set by a momentary glitch during the self-test, so always check for pending codes and repeat the self-test after clearing to avoid chasing a ghost.
  • Aftermarket remote starters or alarm systems that tap into the A/C clutch circuit can back-feed voltage and trigger P1464, so inspect for non-factory wiring.
  • On some Ford models, the ACCS signal is a duty cycle or variable voltage rather than a simple on/off, so a digital multimeter may not show the fault; use a lab scope for accurate diagnosis.

Can I keep driving with P1464?

You can usually continue driving with P1464 because it primarily affects the air conditioning and does not compromise engine safety or drivability. Avoid using the A/C until the fault is repaired, and if you notice the compressor not engaging or unusual noises, have it checked promptly to prevent secondary damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Ford vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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