P0999: Shift Solenoid F Control Circuit High
What to do
Expect specific gears to be missing. Ask for the winding to be measured rather than the solenoid replaced on the strength of the code — a broken wire reads identically and costs a fraction as much.
What this code means
Shift solenoid F's control circuit reads above its valid range — an open circuit or a short to supply, indistinguishable at the module. Measuring the winding directly separates a failed solenoid from a broken wire.
This is the last of the P0 range's decimal-numbered codes, and a fitting one to pause on: the same short list of causes that has explained hundreds of circuit faults across the whole corpus — an open wire, a corroded connector, a failed winding, a short to supply. However complex the machine in front of them, most electrical faults on a vehicle are still one of those four, and the discipline of measuring rather than assuming is what separates them.
Likely causes
Start here
- Open circuit in solenoid wiring · moderate
- Failed shift solenoid · moderate
- Corroded transmission connector · moderate
Less common
- Wiring shorted to voltage · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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