What it means
The voltage B feedback of the electric A/C compressor motor is above the expected window. Phase wire shorted to B+ or driver fault.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The control system monitors voltage feedback B for the electric A/C compressor motor. P2D43 sets when the signal is above its expected window, which can result from phase B wiring shorted to battery positive or a faulty high-side output driver.
Common causes
Most likely first.
- Phase B wire shorted to B+
- Output driver high-side fault
Symptoms
- A/C warning or check-engine light
- Reduced or no cabin cooling
- A/C may switch off
How to diagnose it
- Record freeze-frame data and check voltage B feedback alongside compressor commands to confirm when the high reading occurs.
- With the vehicle powered down according to the manufacturer's procedure, inspect phase B wiring and connectors for chafing against power wiring or signs of heat damage.
- Use the wiring diagram and specified safe test procedure to check whether the phase B circuit is shorted to battery positive.
- Inspect the compressor control module connector and harness for damaged terminals or unintended power feeds.
- If no harness short is found, test the high-side output driver and compressor circuit against the manufacturer's specification.
Common fixes
- Repair phase B wiring shorted to battery positive.
- Repair or replace damaged connectors or terminals causing unintended power contact.
- Replace a damaged section of the compressor harness.
- Replace a confirmed faulty high-side output driver or control module.
Can I keep driving?
Driving is generally possible if the vehicle has no other warnings, but the compressor may be disabled and cabin cooling lost. Do not depend on A/C for defogging when visibility is at risk, and stop if hybrid-system warnings or reduced power occur.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.