P037A code meaning
Glow Plug/Heater Indicator Control Circuit Low
Powertrain system Generic code P03xx codes Check engine light
What P037A means
Diesel engines show the driver a wait-to-start lamp while the glow plugs preheat; the engine module switches it with a high-side driver. P037A means the lamp control circuit is too low – in practice a short to ground on the line to the instrument cluster. GM's diesels detect it in the driver itself: about 0.5 Ω to ground with the lamp commanded, only with a lamp configured, ignition on, more than 11 V and not while cranking. The 2015 engines need 3 s of fault, the 2016/2018 engines 10 of 15 samples; the check engine light follows after two trips. The glow plugs keep working; only the indication is missing, so the driver may start too early. CARB requires monitoring of the wait-to-start lamp circuit. Ford reports lamp faults under P0381 and does not use P037A.
P037A at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P037A
- Glow plug light does not come on or stays dim
- Check engine light on (GM after two trips)
- Driver starts too early, possibly poor cold start
Common causes of P037A
- Most likelyLamp control wire chafed through to ground between engine module and cluster
- PossibleLamp or LED driver in the instrument cluster shorted internally
- PossibleMoisture or corrosion in the module or cluster connector
- Less likelyDriver in the engine module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Glow plug indicatorIndicator wiringInstrument clusterEngine control module
What each part of P037A means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 3 | Area: ignition system or misfire. |
| 7A | The exact fault in that area. |
What to do next
- Note P037A and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P037A
What does P037A mean?
P037A means "Glow Plug/Heater Indicator Control Circuit Low". Diesel engines show the driver a wait-to-start lamp while the glow plugs preheat; the engine module switches it with a high-side driver. It is a generic code, so it means the same on every make.
Is it safe to drive with P037A?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P037A fail an emissions test?
Yes, it can. P037A is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P037A to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P037A clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.