P2AF4: Starter Relay C Control Circuit High

What it means

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

At a glance

• Usually lights the check-engine light

How it works

Starter relay C is an electrically controlled switch in the cranking circuit. The module monitors its control circuit and sets P2AF4 when the circuit level is higher than expected, which can result from a short to battery voltage, an open relay coil, or poor terminal contact.

Common causes

Most likely first.

1. Control wire shorted to B+
2. Open 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. Record freeze-frame and related starting-system codes, and note whether the fault occurs during a failed or intermittent start.
2. Inspect relay C's connector and harness for damaged insulation touching a power feed, corrosion, or loose pins.
3. Confirm relay C's location and seating from the vehicle's fuse-box diagram, then check its terminals for heat or corrosion.
4. Use the manufacturer's wiring diagram to test the relay C control wire for a short to battery voltage.
5. If the harness is sound, test the relay coil and commanded circuit according to the manufacturer's procedure for an open coil.

Common fixes

• Clean or repair corroded relay C connector terminals.
• Repair the control wire if it is shorted to a power feed.
• Replace relay C if its coil is open.

Can I keep driving?

Starting may be unreliable, and an unexpected no-crank can leave you stranded. If the vehicle starts and the starter disengages normally, a short drive is generally possible, but have the circuit checked soon.