P069C: Cylinder 10 Glow Plug Control Circuit Low

Modern diesel glow systems switch each glow plug through its own power semiconductor (in a glow plug module or the engine module), so current and faults can be measured per plug; a faulty channel is switched off. CARB requires glow plugs to be checked for correct current and voltage drop and, since model year 2010, a single plug outside specification to be detected and named. P069C means the circuit to the cylinder 10 glow plug is shorted to ground or draws overcurrent. GM's engine-module drivers flag an impedance to ground below 0.11 Ω (10 of 20 samples) with the check engine and glow plug lamps after two trips; Ford's 2023 Power Stroke checks during heating for more than 22 A for 0.3 s or 20–22 A for 2 s. The channel is switched off and plug 10 no longer heats – harder cold starts and white smoke follow. No manufacturer document available to us uses this code for cylinders 9 and above; the description follows cylinders 1–8.

Low severity. Can I keep driving?You can keep driving, although cold starts will be harder. Avoid cranking the starter repeatedly on cold days.

Cylinder 10 is numbered according to the manufacturer: check your engine's manual before working on it.

Symptoms

Check engine and glow plug lamp
Harder cold start, especially in frost
Rough running and white smoke right after a cold start

Most likely causes

Glow plug cylinder 10 shorted internally (element against body)
Plug wire insulation damaged and shorted to ground
Wrong plug type (resistance or voltage rating)
Driver in the glow or engine module faulty, or software (GM bulletins)

What to check, in order

Start with the simplest. You can tick off each step.

Check the fuse and connector
With the connector unplugged, check whether the signal wire is making contact with ground.
Measure the resistance of each glow plug with the engine cold
Check the power supply during the preheat cycle
Test the module or relay if the glow plugs are good

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P069C means

P: Powertrain: engine and transmission
0: Generic code: same on every make
6: Control modules and outputs
9C: Specific fault in that system

Frequently asked questions

Can I keep driving with code P069C?

You can keep driving, although cold starts will be harder. Avoid cranking the starter repeatedly on cold days.

What causes code P069C?

The most common causes are: glow plug cylinder 10 shorted internally (element against body); plug wire insulation damaged and shorted to ground; wrong plug type (resistance or voltage rating).

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.