P0804: Upshift/Skip Shift Lamp Control Circuit

What it means

General electrical fault on the upshift/skip-shift indicator lamp control circuit — the dashboard light that prompts the driver to skip from 1st straight to 4th. With the input invalid the lamp cannot be illuminated.

At a glance

• Usually lights the check-engine light

How it works

The skip-shift indicator circuit controls the dashboard lamp that prompts a driver to shift from first directly to fourth when the feature is available. P0804 sets when the module detects an electrical fault in that lamp-control circuit, so the prompt may not illuminate.

Common causes

Most likely first.

1. Open or shorted lamp wire
2. Failed lamp bulb or LED

Symptoms

• Skip-shift indicator may not operate
• Check-engine light may be on

How to diagnose it

1. Scan for related codes and save freeze-frame data to see whether the fault occurred while the skip-shift feature was active.
2. Check the dashboard indicator during the vehicle’s skip-shift prompt conditions, if those conditions can be confirmed safely.
3. Inspect the skip-shift lamp, its connector, and the associated wiring for damage, loose terminals, or corrosion.
4. Test the lamp and control circuit for opens and shorts, following the wiring diagram and manufacturer’s specification.
5. If the lamp and wiring pass, check the control-module output and connector.

Common fixes

• Reconnect or clean a loose skip-shift lamp connector.
• Replace a failed indicator bulb or LED where serviceable.
• Repair an open or short in the lamp-control wiring.
• Repair a confirmed control-module output fault.

Can I keep driving?

If the transmission operates normally, driving is generally possible, but you may not receive the skip-shift prompt. Do not rely on the indicator until it works; stop driving if other transmission symptoms appear.