P0804 Code: Meaning, Symptoms, Causes & Fix

Overview

Symptoms

• harsh or delayed shifting
• reduced acceleration
• gear hunting

Common causes

• Disconnected or loose connector affecting 1-4 upshift (skip shift) lamp control circuit malfunction
• Open circuit in wiring
• Connector pin damage/corrosion or harness stress near related components

How to diagnose P0804

1. Confirm P0804 and capture freeze-frame data with a professional scan tool.
2. Inspect wiring, connectors, and grounds related to 1-4 upshift (skip shift) lamp control circuit malfunction for obvious defects.
3. Use a continuity test from module pin to component to identify opens/high resistance.
4. Check for related DTCs to identify the root-cause chain before replacing parts.
5. After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P0804

Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.

Can you drive with P0804?

Most vehicles can be driven short-term with P0804, but postpone heavy load/highway driving until repaired.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

1. Repair obvious wiring/connector faults first to prevent repeat parts replacement.
2. Address the root fault mode (open) in the 1-4 upshift (skip shift) lamp control circuit malfunction circuit/system.
3. Apply the required relearn/adaptation procedure if specified by service information.
4. Road-test and verify P0804 remains cleared under the conditions that originally set the code.

Fix options

• Repair open circuit and secure connector lock.
• Clear corrosion and protect terminals.
• Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$300-$1500

Common mistakes when diagnosing P0804

• Replacing parts without verifying voltage, ground, and signal integrity first.
• Ignoring related stored/pending codes that indicate upstream faults.
• Skipping post-repair verification drive cycle and readiness checks.

P0804 in common vehicles

P0804 appears across makes such as Mazda, Subaru, Lexus, Jeep. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P0804?

P0804 is commonly set by open faults affecting 1-4 upshift (skip shift) lamp control circuit malfunction.

How much does it cost to fix P0804?

For P0804, repair costs are typically $300-$1500 depending on exact root cause, labor rates, and part quality.

Can I clear P0804 without repair?

You can clear P0804 temporarily, but the code usually returns until the underlying fault is corrected.

Helpful tools

• Estimate repair cost
• Decode your VIN
• Calculate fuel cost