P0800
Transfer Case Control System (MIL Request)
The transfer case control module has requested the ECM/PCM to illuminate the MIL because of a fault on its side that is emissions- or driveline-relevant. The original fault is in the transfer case module itself.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Internal fault in transfer case module — read its DTCsCommon
Parts involved
- Transfer Case Module
P0800 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.