A/C Request Circuit Range/Performance
The P255F code indicates that the Powertrain Control Module (PCM) has detected an issue with the A/C request circuit, specifically a range or performance problem. This circuit carries the signal from the A/C control head to the PCM, requesting compressor engagement. The PCM monitors this signal to manage engine load and cooling. A fault can prevent the A/C from operating correctly or cause erratic behavior.
01. Most Common Causes
- Faulty A/C pressure sensor
- Open or short in A/C request circuit wiring
- Failed A/C control module or head unit
- Corroded or loose electrical connectors
02. Symptoms You Will Notice
- A/C system inoperative or intermittent operation
- Check Engine Light illuminated
- A/C compressor not engaging
- Reduced cooling performance
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Visually inspect A/C request circuit wiring and connectors for damage or corrosion.
Step 3: Test A/C pressure sensor signal voltage with a multimeter and compare to specifications.
Step 4: Check A/C control module output signal to PCM using a scan tool or oscilloscope.
Step 5: Perform a circuit continuity test between A/C control module and PCM.
04. Commonly Affected Makes
05. 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 engine performance problems, have it checked soon.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and repair, depending on the root cause. Parts like a pressure sensor or relay are inexpensive, but labor adds cost.