P2AF8: Starter Relay D Control Circuit Low

What it means

Starter relay D reports a control circuit low condition. Engine cranking can be inhibited or commanded unintentionally.

At a glance

• Usually lights the check-engine light

How it works

Starter relay D controls a separate part of the starting system when the module requests cranking. The module sets P2AF8 when relay D's control circuit reads lower than expected, which can be caused by a short to ground, a shorted relay coil, or poor connector contact.

Common causes

Most likely first.

1. Control wire shorted to ground
2. Internal short in relay coil
3. Connector pins corroded - high contact resistance

Symptoms

• Check-engine light may be on
• Engine may not crank
• Intermittent starting difficulty

How to diagnose it

1. Check freeze-frame and related starting-system codes, and note whether the low reading occurs with a no-crank or intermittent start.
2. Inspect relay D's connector and harness for chafing to ground, corroded pins, or loose terminals.
3. Locate relay D from the vehicle's fuse-box diagram and check that it is seated and its socket is undamaged.
4. Using the manufacturer's wiring diagram, test relay D's control wire for a short to ground and verify connector continuity.
5. Test relay D's coil and control response using the manufacturer's procedure to identify an internal coil short.

Common fixes

• Clean or repair corroded relay D connector terminals.
• Repair relay D's control wire where it is shorted to ground.
• Replace relay D if its coil is internally shorted.

Can I keep driving?

Starting may be unreliable and the engine could fail to crank, so avoid depending on the vehicle where a failed restart would be hazardous. If it starts normally, a short drive may be possible, but arrange prompt diagnosis.