A/C Request Circuit Range/Performance
The P256F code indicates that the Engine Control Module (ECM) has detected an issue with the A/C request circuit, which communicates the driver's A/C on/off request to the ECM. This circuit typically involves the A/C switch, pressure sensors, and wiring. The ECM monitors the voltage or signal from the A/C request circuit and compares it to expected values. When the signal is out of range or not performing as expected, the code is set. This can prevent the A/C compressor from engaging, leading to no cold air.
01. Most Common Causes
- Faulty A/C request switch or sensor
- Open or shorted wiring in the A/C request circuit
- Corroded or loose electrical connectors
- Failed A/C pressure sensor
- ECM software or hardware issue
02. Symptoms You Will Notice
- A/C system does not blow cold air
- A/C compressor does not engage
- Check Engine Light illuminated
- Intermittent A/C operation
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for related codes.
Step 2: Inspect the A/C request circuit wiring and connectors for damage, corrosion, or loose connections.
Step 3: Test the A/C request switch/sensor with a multimeter to ensure proper operation.
Step 4: Check the A/C pressure sensor signal and compare to specifications.
Step 5: If all else is fine, update or reprogram the ECM as per manufacturer service bulletins.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, it is generally safe to drive, but the A/C will not work, which can be uncomfortable in hot weather. The underlying issue should be diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on the cause. Replacing a switch or sensor may cost more if parts are expensive.