OBD Codes

P0800

Transfer Case Control System (MIL Request)

Severetransmission

Overview

The P0800 diagnostic trouble code signals a transfer case control system (mil request) condition detected by the transmission control module. This code relates to the automatic transmission system and may affect shift quality, timing, or overall transmission performance. Prompt attention is important to prevent further transmission damage.

Symptoms

  • Loss of one or more gears
  • Harsh or delayed shifting
  • Shuddering or vibration during acceleration
  • Check Engine Light (MIL) illuminated

Common Causes

  • Faulty input or output speed sensor
  • Faulty shift solenoid or solenoid pack
  • Faulty transmission control module (TCM)
  • Low or contaminated transmission fluid

Diagnosis Steps

  1. 1Connect an OBD-II scanner and read all stored trouble codes and freeze frame data
  2. 2Check transmission fluid level and condition; top off or replace if needed
  3. 3Test the transmission speed sensors with a multimeter or scan tool
  4. 4Inspect wiring and connectors for the transmission harness
  5. 5Perform a transmission pressure test if accessible

Estimated Repair Cost

$300$2,500

Cost varies by vehicle, location, and repair shop. Includes parts and labor.

Commonly Affected Vehicles

Honda AccordFord F-150Ford ExplorerToyota Camry

Related Codes

More Transmission Codes

Frequently Asked Questions

Driving with a transmission code is risky. Continued driving can cause further damage to the transmission, resulting in significantly higher repair costs. Have it inspected as soon as possible.