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Code

Generic P — Powertrain

Starter Relay D Stuck On

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 36 RU: 26

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Page language: EN

Causes

Stuck or welded relay contacts
Short to battery on the relay control or power feed
Faulty relay coil or internal short
Damaged wiring or connector (pinched, corroded, chafed)
Faulty body/engine control module that drives the relay
Incorrect or intermittent ground at relay or control module

Symptoms

Starter continues to crank or engages intermittently when ignition is OFF or in RUN
Parasitic battery drain with ignition off
Starter engages without key or out of gear (safety risk)
No start or erratic start behavior
Associated warning lights or other DTCs present

What to check

Read and record freeze frame and pending codes; check for other related DTCs
Visually inspect starter relay D, its socket, harness, and connector for corrosion, heat damage, or melted plastic
Verify fuse(s) for starter and relay power are intact and correct rating
Check for aftermarket items tied into starter circuit (alarms, remote starters)
Observe starter operation while turning key through positions with a second person to recreate symptom (use safe procedures)

Signal parameters

Control/coil terminal (relay D) inactive: 0 V (or near 0 V with respect to chassis ground) expected when off
Control/coil terminal active: battery voltage (~12.0–14.5 V) when commanded on
Coil resistance (typical relay): 50–200 ohms (varies by relay); consult spec for exact value
Power feed terminal: battery voltage (approx. 12.0–14.5 V) at all times
When off, continuity between battery feed and starter circuit should be open (no continuity)

Diagnostic algorithm

Safety first: park vehicle in neutral/park, set parking brake, disconnect battery if required for component removal. Take care with starter circuits (risk of engine cranking).
Scan: retrieve all codes and freeze frame. Note ignition state and voltage when code set.
Visual: inspect Relay D, socket, harness, and related fuses for damage or corrosion.
Swap test: if identical relays present, swap Relay D with a known-good relay (same type) and see if code and symptom follow relay. If they do, replace relay.
Backprobe: with key OFF, backprobe relay control terminal and relay power terminal. Confirm power terminal has battery voltage and control terminal is 0 V when off. If control terminal shows battery voltage with command OFF, there is a stuck-on drive or short to battery.
Command test: command starter/ignition (START/RUN) while monitoring control wire. Confirm control module only applies voltage when commanded. If module is commanding when it should not, suspect control module or software; verify against inputs (ignition switch, clutch/park switch).
Resistance/current test: remove relay and measure coil resistance. If shorted or open, replace relay. Measure current draw from starter circuit when relay is engaged (if safe to do) to ensure not excessive.
Wiring check: with relay removed, check for continuity to starter and for shorts to battery or ground on the control circuit. Wiggle harness while monitoring to find intermittent faults.
Module output: if wiring is good and relay is good, check driver output at control module for shorted transistor (sourcing battery) using oscilloscope or DVOM. Refer to manufacturer procedures before replacing module.
Repair and verify: repair or replace failed component (relay, wiring, connector, control module). Clear codes, perform functional verification and road test to confirm symptom is resolved.