The P0804 trouble code indicates a malfunction in the 1-4 upshift (skip shift) lamp control circuit. Here’s what you should know:
P0804 1-4 Upshift (Skip Shift) Lamp Control Circuit Malfunction
Code symptoms P0804.
1. Illumination of the Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL) on the dashboard.
2. The skip shift indicator lamp may not function properly, failing to illuminate or staying illuminated incorrectly.
3. Other transmission-related symptoms such as harsh shifting or slipping may occur, depending on the underlying cause.
Causes of the code P0804.
1. Faulty 1-4 upshift (skip shift) lamp.
2. Wiring or connector issues in the lamp control circuit.
3. Corrosion or poor connections in the circuit.
4. A defective transmission control module (TCM) or powertrain control module (PCM).
Code Solutions P0804.
1. Use an OBD-II scanner to retrieve freeze frame data and any other stored trouble codes. This information can provide insight into when and how the malfunction occurred.
2. Inspect the wiring and connectors in the 1-4 upshift lamp control circuit for damage, corrosion, or loose connections. Repair or replace any damaged components as needed.
3. Test the skip shift indicator lamp itself for proper operation. This may involve applying battery voltage and ground directly to the lamp terminals to see if it illuminates.
4. Test the lamp control circuit for continuity and proper voltage using a multimeter. If the circuit is open or has voltage issues, further diagnosis is necessary to determine the cause.
5. If the wiring and connectors check out okay, test the TCM or PCM for proper operation. This may involve using a diagnostic scan tool to communicate with the module and retrieve any stored trouble codes or data.
6. Clear the trouble codes from the vehicle’s computer memory and test the skip shift indicator lamp to see if it functions properly. If the code returns or the lamp still doesn’t work correctly, further diagnosis or repairs may be required.