P2D66 code meaning
Battery Charging System Negative Contactor C Control Circuit Range/Performance
What P2D66 means
P2D66 flags a coil circuit of minus charging contactor C that is connected but responds outside its expected band while showing neither a break nor a short. P2D66 is not described by any manufacturer, and GM's public tables list no range test for charge contactor coils. A GM patent shows why such a check needs care: the coil current of the same contactor differs markedly between -40, 25 and 85 °C, so the patent compares readings with a reference stored offline for each contactor. CARB requires output parts that a maker monitors on a hybrid to respond properly to commands. Corroded terminals and an aged coil fit this pattern. P2D65 is the open, P2D67/P2D68 low and high, P2D5F the plus side.
P2D66 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor1 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2D66
- Charging via contactor C drops out now and then
- Fault occurs mainly in very cold or very hot conditions
- Code returns after clearing
Common causes of P2D66
- Most likelyCorroded or loose terminals raising circuit resistance
- PossibleCoil resistance drifted through ageing or overheating
- Less likelyModule software with an unsuitable reference or calibration
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Bcs neg contactor cWiring harnessBms
What each part of P2D66 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 66 | The exact fault in that area. |
What to do next
- Note P2D66 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 P2D66
What does P2D66 mean?
P2D66 means "Battery Charging System Negative Contactor C Control Circuit Range/Performance". P2D66 flags a coil circuit of minus charging contactor C that is connected but responds outside its expected band while showing neither a break nor a short. It is a generic code, so it means the same on every make.
Is it safe to drive with P2D66?
P2D66 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P2D66 fail an emissions test?
P2D66 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P2D66 to fix?
Difficulty: workshop only. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will P2D66 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.