P2691 code meaning
Cylinder 6 Injector Data Incompatible
Powertrain system Generic code P26xx codes Check engine light
What P2691 means
P2691 refers to the injector in cylinder 6. For six-cylinder diesels it is the last of the per-cylinder codes: GM's 2025 table 25OBDG04B stops at P2691, while the V8 table 25OBDG04A goes on to P2693. In both 2025 tables the check is always active on production controllers and fails if the end-of-line adjustment value was never written; as a further guard, a separate plausibility test under P060C looks at the size of the computed adjustment values. GM rates P2691 Type A. Ford's 2023 diesel summary lists it for its 3.0 L and 6.7 L engines. Programming the code printed on the cylinder 6 injector normally clears it; a recurring fault after correct entry points to the controller.
P2691 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2691
- Check engine light on
- Possible knock or smoke from the affected cylinder
Common causes of P2691
- Most likelyCylinder 6 injector code missing after replacement
- PossibleEntered value rejected as implausible by the software
- Less likelyController memory fault losing stored injector data
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector cyl6Control module
What each part of P2691 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 6 | Area: computer (engine control module) and output circuits. |
| 91 | The exact fault in that area. |
What to do next
- Note P2691 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 P2691
What does P2691 mean?
P2691 means "Cylinder 6 Injector Data Incompatible". P2691 refers to the injector in cylinder 6. It is a generic code, so it means the same on every make.
Is it safe to drive with P2691?
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 P2691 fail an emissions test?
Yes, it can. P2691 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 P2691 to fix?
Difficulty: medium. A typical repair takes 0.3 to 1.5 hours of work. This is a job for a workshop.
Will P2691 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.