P2156 code meaning
Fuel Injector Group D Supply Voltage Circuit Low
Powertrain system Generic code P21xx codes Check engine light
What P2156 means
P2156 reports the fourth shared injector supply shorted toward ground. GM's 2018 Duramax uses it only on the 6.6 L V8, where bank 4 combines injectors 3 and 8; the high-side pin reading 0.5 Ω or less to ground while switched on sets it after 5 of 10 samples, type A, lamp on the first trip. Ford's 2023 diesel summary stops at group C, so the code does not appear there. On GM gasoline direct injection, as in the Saab 9-5 2.0T, P2156 stands for low voltage on the high-side control line of cylinder 4, set after 1 s and handled as type B. Since the diesel bank feeds two injectors, two cylinders cut out at once and the engine shakes noticeably. P2155 marks an open circuit and P2157 a high fault in the same group.
P2156 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2156
- Two cylinders misfire together
- Strong vibration and power loss
- Check engine lamp on immediately
Common causes of P2156
- Most likelyGroup D supply wire chafed and shorted to ground
- PossibleInjector of group D shorted to its body
- PossibleMoisture in the injector harness connector
- Less likelyFaulty injector driver in the engine control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injectorInjector wiringEngine control module
What each part of P2156 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 1 | Area: fuel and air metering. |
| 56 | The exact fault in that area. |
What to do next
- Note P2156 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 P2156
What does P2156 mean?
P2156 means "Fuel Injector Group D Supply Voltage Circuit Low". P2156 reports the fourth shared injector supply shorted toward ground. It is a generic code, so it means the same on every make.
Is it safe to drive with P2156?
Drive gently and only to a workshop. With P2156 the car can go into limp mode (reduced power) to protect itself.
Will P2156 fail an emissions test?
Yes, it can. P2156 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 P2156 to fix?
Difficulty: hard. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will P2156 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.