P0680

Code

Generic P — Powertrain

Cylinder 10 Glow Plug Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 39 RU: 23

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Failed (open or internally high-resistance) glow plug at cylinder 10
Open or corroded connector at the glow plug
Broken, pinched or chafed wiring in the glow-plug harness (open circuit)
Blown fuse or faulty glow-plug relay/driver supplying the circuit
High-resistance ground at engine block or glow-plug return path
Faulty PCM/ECM driver (open or stuck)

Symptoms

Longer cranking or hard starting when cold
White or blue smoke on cold start, or rough idle until warmed
Glow-plug warning lamp or glow indicator illuminated (depending on vehicle)
Check Engine Light / MIL illuminated
Possible reduced cold-engine power or increased emissions

What to check

Scan tool: read freeze-frame data and DTC history and confirm P0680 presence
Compare live glow-plug current or status for all cylinders (if available)
Visually inspect glow-plug connector, wiring harness and engine ground near cylinder 10
Check relevant fuses and glow-relay operation
Measure voltage at the glow-plug connector with ignition ON and during cranking
Measure resistance of the glow plug (bench test) and compare to specification

Signal parameters

Glow plug DC resistance (typical range): ~0.5 – 2.0 ohms (verify exact spec for vehicle)
Supply voltage to glow plug when energized: near battery voltage (11–14.5 V)
Typical current draw per glow plug: several amps (varies by design) — expect measurable current when energized
Open-circuit: infinite/very high resistance; short-to-ground: near 0 ohms
PCM output is either switched supply or ground driver depending on design — check wiring diagram

Diagnostic algorithm

Read and record DTC and freeze-frame data with a scan tool. Confirm P0680 is current or stored.
Inspect visible wiring and connector at cylinder 10 for corrosion, loose pins, melted insulation, or mechanical damage.
Verify relevant fuses and glow-relay operation. If relay is suspected, check coil and contacts and replace if faulty.
With ignition OFF, disconnect the glow-plug connector and measure glow-plug DC resistance to engine block or between terminal and body. Compare to spec. If open or out of range, replace the glow plug.
With connector still disconnected, check continuity from the connector terminal back to the PCM/ECM glow-driver pin. Repair any open or high-resistance sections.
With back-probing and appropriate safety, turn ignition ON and measure voltage at the connector during the preheat cycle and during crank. Confirm proper voltage/switching.
If voltage is present but plug resistance is correct and still not operating, measure current draw when connector is connected (use clamp meter on feed or test harness). Low or no current with correct voltage indicates open at plug or connector; correct current but no heat suggests bad plug.
If wiring and glow plug check out, verify PCM driver operation by checking switching to ground or supply as per wiring diagram. Replace PCM only after confirming an external wiring/relay issue is not present.
Repair or replace faulty component(s) (connector, wiring, relay, fuse, glow plug). Clear codes and perform a test start and re-scan for reappearance.
If intermittent, perform wiggle tests and road/start cycles to confirm repair. Document any replaced parts and final test results.

Likely causes

Individual glow plug failure (most common)
Connector corrosion or wiring damage near the cylinder head
Failed glow-relay or fuse affecting just that circuit
PCM driver failure (less common) — confirm wiring before replacing module

Fault status

⚠️ Status

Stored when the ECM/PCM detects an open or high-resistance condition in the Cylinder 10 glow plug circuit (no proper voltage/current detected to the glow plug). May set MIL and cause hard starting or increased smoke during cold starts.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5 - 2.5 hours