P2691: Cylinder 6 Injector Data Incompatible
What to do
As at P2690 — if this followed injector work, nothing is broken and a calibration code has not been entered, or has been entered wrongly.
Expect uneven idle, a harder knock from one cylinder and some smoke until it is sorted.
One thing worth asking about specifically if your engine is a V6: was the cylinder numbering confirmed? Cylinder 6 is not necessarily the one at the end of a bank — the numbering follows the manufacturer's convention rather than the physical layout, and a code entered against the wrong cylinder puts two of them out at once rather than one.
Go back to whoever fitted the injectors and ask for the coding to be checked.
What this code means
The calibration data held for cylinder 6's injector does not match the injector fitted there, or is absent. What injector calibration codes are and why they must be entered per cylinder is explained in full at P2690.
On a six-cylinder engine this is the last cylinder, and that position makes one cause disproportionately likely: it is the one most often left until last and most often rushed. Injector replacement on an inline six means working progressively along the head, and the final injector is fitted when access is worst, the light is going and the job is nearly done. Both the fitting and the code entry are more error-prone at that point, which is why a single-cylinder coding fault on the last cylinder of a set is a recognisable pattern rather than a coincidence.
The other consideration specific to a six is bank identification. On a V6 the cylinder numbering is not the physical order along either bank, and cylinder 6 may sit anywhere depending on the manufacturer's convention. Entering a code against "the last injector fitted" rather than against the cylinder the module means is a straightforward way to get two cylinders wrong at once — so the numbering should be confirmed against the manufacturer's diagram, not inferred from the layout.
Likely causes
Start here
- Injector fitted without entering its calibration code · specialist
- Injector calibration code entered incorrectly · specialist
Less common
- Injectors swapped between cylinders · specialist
- Engine control module replaced or reprogrammed · specialist
- Interrupted module programming · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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