P0800: Transfer Case Control System (Malfunction Indicator Lamp Request)
What to do
This code names no fault — it says the transfer case module has one to report. Ask for the codes stored in the transfer case control module specifically; a scan of the engine module alone will show only this request. Four-wheel-drive behaviour changing (refusing to engage, binding on tight turns) is the system's side of the same story.
What this code means
The transfer case control module has asked for the warning lamp — P0700's argument on a different module. This is the record of a request, not a description of what is wrong, and the code naming the actual fault is stored in the transfer case module itself.
This code only exists on four-wheel-drive and all-wheel-drive vehicles, because only they carry a transfer case and a module to run it. That makes the misdirection specific: a basic code reader shows this alone, which reads like a transmission fault — and on a 4x4 an unexplained "transmission" warning invites expensive guesses at a gearbox that is fine. The module with something to say is the one dividing drive between the axles.
Everything else on the P0700 page applies and is not repeated: the request tells you where to look, never what is wrong, and clearing it without reading the transfer case module's own codes erases the address while leaving the fault.
Likely causes
Start here
- Fault stored in a secondary driveline module · specialist
Less common
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.
Sign in or create an account to add what you found about P0800.