P2548 critical

Throttle Control Relay Circuit High

The P2548 code means the vehicle's onboard diagnostic system has detected: Throttle Control Relay Circuit High. This is a critical severity code.

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Keep driving?
Short distances only
DIY difficulty
moderate
Estimated cost
$100 - $450 (parts and labor)
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Common Symptoms

  • Throttle body always powered even with ignition off
  • Potential battery drain
  • Check engine light on
  • Throttle may respond normally while running

Probable Causes (Ranked by Likelihood)

  • Short to voltage in relay control circuit Very High
  • Relay contacts welded closed High
  • Aftermarket wiring providing constant power Moderate
  • ECM relay driver stuck high Low

Step-by-Step Diagnostic Procedure

  1. Check for voltage at relay with ignition off

  2. Inspect relay contacts for welding

  3. Test control circuit for short to battery voltage

  4. Remove aftermarket electrical accessories from throttle circuit

Frequently Asked Questions

Can P2548 cause a battery drain?

Yes. If the throttle control relay stays energized, the throttle body motor remains powered, causing a parasitic draw that can drain the battery.

Is it safe to drive with P2548?

The throttle may respond normally while driving, but the constant power condition poses a battery drain risk and the ECM cannot properly manage the throttle safety system.

How do I know if the relay contacts are welded?

Remove the relay and check for continuity across the load terminals with no power applied. If there is continuity, the contacts are fused together.

Sources

This page is built from documented references. Verify against your own service info before repair work.

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