P0681

Code

Generic P — Powertrain

Cylinder 11 Glow Plug Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 47 RU: 33

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Page language: EN

Causes

Failed glow plug (open element)
Broken or corroded wiring or connector at glow plug 11
Poor or missing ground at glow plug or harness
Faulty glow plug relay/module or driver in ECM
Blown fuse or supply circuit open to glow system
Internal ECM/PCM driver fault

Symptoms

Hard starting, especially when cold
Longer crank time before start or extended white smoke on cold start
Illuminated glow plug/SES/MIL lamp
Rough idle or misfire at cold start (less common once engine warm)
Stored fault code(s) related to glow/heater circuit

What to check

Scan for stored and pending codes; note freeze-frame and battery voltage
Visually inspect glow plug 11 connector and wiring for damage, corrosion, or disconnection
Check glow plug fuse(s) and relay operation
Measure resistance of glow plug 11 (engine cold) at the plug
Back-probe connector and verify supply voltage and control signal when glow is commanded

Signal parameters

Battery/supply voltage present at glow plug harness: ~11–14 V (when ignition on/relay closed)
Glow plug resistance typical: 0.2–5 ohms (varies by design) — open = infinite/OL
PCM/ECM control output: switched ground or switched 12 V depending on design when glow is commanded
Current draw per glow plug: typically 2–20 A (varies by design); an open circuit will show near 0 A

Diagnostic algorithm

Retrieve codes and freeze-frame data. Note battery voltage and engine conditions when the fault set. Check for other glow/heater codes.
Visually inspect the glow plug 11 connector, wiring harness, and pins for corrosion, bent pins, broken wires, or heat damage. Repair any obvious issues.
With ignition off, disconnect the glow plug connector and measure resistance of glow plug 11 to engine ground. Compare to specification; an open (infinite) or very high resistance indicates a failed glow plug.
Inspect and test fuses and glow plug relay(s). Verify relay activation during glow command; listen for relay click or check with a test light/voltmeter.
With harness connected, back-probe the supply and control wires at the glow plug connector. Have an assistant request glow/heater ON (or use diagnostic active test). Verify supply voltage and that the ECM provides the expected control (switch to ground or to battery) while commanded.
If supply is present but control is absent, trace control wiring back to relay/ECM. Check continuity and resistance of wiring to the ECM or relay. Repair any open or shorted wiring.
If control output from ECM is commanded but glow plug does not draw current (and plug resistance was bad), replace glow plug 11 and retest.
If wiring and glow plug check good but no current flow and relay/fuse are OK, suspect a faulty relay/module or ECM output stage. Verify relay driver and, if required, bench-test or replace relay/module per manufacturer procedures.
After repairs, clear codes, perform a glow function test, and confirm code does not return during subsequent cold starts and that freeze-frame conditions are resolved.

Likely causes

Open or high-resistance glow plug in cylinder 11
Disconnected or damaged harness/connector at cylinder 11
Corroded terminal or poor crimp causing intermittent/open circuit
Failed glow plug control relay or fuse
Driver output damage in ECM after short/high current

Fault status

⚠️ Status

PCM detected an open or interrupted glow plug/heater circuit for cylinder 11. The fault may cause hard starting and will set a diagnostic trouble code and illuminate the warning lamp.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours