A/C Request Circuit Range/Performance
The P256F code indicates that the Powertrain Control Module (PCM) has detected an issue with the A/C request signal circuit. This circuit carries a voltage signal from the A/C control head to the PCM, requesting compressor engagement. The code sets when the signal is out of the expected range or performance parameters, often due to a faulty A/C pressure sensor, wiring issues, or a malfunctioning A/C control module.
1. Most Common Causes
- Faulty A/C pressure sensor
- Open or shorted wiring in the A/C request circuit
- Malfunctioning A/C control module
- Corroded or loose electrical connectors
2. Symptoms You Will Notice
- A/C system inoperative or intermittent operation
- Check Engine Light illuminated
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the A/C request circuit wiring and connectors for damage, corrosion, or loose connections.
Step 3: Test the A/C pressure sensor signal voltage with a multimeter and compare to manufacturer specifications.
Step 4: Check the A/C control module for proper operation and communication with the PCM.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but the A/C may not work properly. Driving without A/C is safe, but if the issue causes the engine to run poorly, have it checked promptly.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: a pressure sensor replacement is $100-$250, while wiring repairs may be $100-$300.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.