The P0804: 1-4 Upshift (Skip Shift) Lamp Control Circuit Malfunction refers to an issue in the circuit that controls the indicator lamp for the 1-4 upshift (skip shift) feature. This lamp typically notifies the driver when the skip shift feature is active. The problem may be caused by a faulty control circuit, wiring or connector issues, or a malfunctioning transmission control module (TCM).
P0804 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P0804: 1-4 Upshift (Skip Shift) Lamp Control Circuit Malfunction |
| Is it serious? | No, but it can cause confusion for the driver if the skip shift lamp is not working correctly, potentially impacting driving behavior. |
| Possible causes | – Faulty lamp control circuit for 1-4 upshift – Wiring or connector issues – Faulty transmission control module (TCM) |
| How to diagnose? | – Test lamp control circuit – Inspect wiring and connectors – Replace faulty components if needed |
P0804 Meaning
The P0804 code indicates that there is a problem with the control circuit responsible for the 1-4 upshift (skip shift) indicator lamp. This lamp signals the driver when the skip shift feature is active, helping with fuel economy by skipping certain gears during acceleration. A malfunction in this circuit could lead to the lamp not illuminating properly, causing confusion for the driver.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for additional transmission-related codes that may give further insight into the issue. | OBD-II Scanner |
| Test Lamp Control Circuit | Use a multimeter or diagnostic scanner to test the lamp control circuit for proper function and ensure the circuit is providing the correct signal to the lamp. | Multimeter, Diagnostic Scanner |
| Inspect Wiring and Connectors | Visually inspect the wiring and connectors associated with the lamp control circuit for signs of damage, corrosion, or loose connections. Repair or replace any damaged components. | Flashlight, Multimeter, Safety Gloves |
| Check Transmission Control Module (TCM) | If no issues are found in the wiring or connectors, test the TCM for faults or communication errors that may affect the lamp control circuit. | Diagnostic Scanner, TCM Testing Tools |
| Replace Faulty Components | If any faulty components are found, such as the lamp control circuit or the TCM, replace them with new parts as per manufacturer specifications. | Replacement Parts, Wrenches, Screwdrivers |
| Clear the Code and Test Drive | After replacing or repairing the components, clear the code using an OBD-II scanner and test drive the vehicle to ensure the issue is resolved. | OBD-II Scanner |
| Recheck for Codes | After the test drive, rescan the vehicle to ensure the P0804 code has not returned. | OBD-II Scanner |
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I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko