P2AF5: Starter Relay C Stuck On

What it means

Starter relay C reports a stuck on condition. Engine cranking can be inhibited or commanded unintentionally.

At a glance

• Usually lights the check-engine light

How it works

Starter relay C switches the starter circuit on when commanded and should release when the command ends. The module sets P2AF5 when it detects that relay C remains on, which may be caused by welded contacts, a stuck output driver, or debris preventing the relay from releasing.

Common causes

Most likely first.

1. Relay contacts welded closed
2. Output driver stuck on
3. Carbon or debris buildup preventing free movement

Symptoms

• Check-engine light may be on
• Starter may continue running after the engine starts
• Unusual starter noise

How to diagnose it

1. Check freeze-frame and related starting-system codes, and note whether the starter continues running after the engine starts.
2. If the starter remains engaged, switch the engine off as soon as it is safe and avoid repeated starting attempts.
3. Inspect relay C and its socket for heat damage, contamination, or terminals that could keep the contacts energized.
4. Using the vehicle's wiring diagram, compare the module's relay C command with whether power remains at the relay output after the command ends.
5. Test relay C contacts and the module's output-driver circuit using the manufacturer's procedure to distinguish welded contacts from a stuck command.

Common fixes

• Replace relay C if its contacts are welded or its mechanism is stuck.
• Clean or repair contaminated or damaged relay socket terminals.
• Repair the relay C control circuit or output driver if it continues to command the relay on.

Can I keep driving?

Do not continue driving if the starter keeps running after the engine starts; stop safely and switch off the engine because the starter and wiring can overheat or be damaged. Have the fault addressed before further use.