P0638: How to Diagnose & Fix — Throttle Actuator Control Range/Performance Bank 1
2 vehicles · 2 makes · $200-$600 repair
How to diagnose and fix P0638: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Volvo XC70 · 2001–2004
The ETM fails due to internal solder joint cracking, causing reduced power, limp mode, and check engine light. This is the same issue that affects all Volvo P2 platform vehicles (S60, V70, XC70). Volvo extended warranty coverage in some markets.
Common Symptoms
- Reduced engine power
- Limp mode
- Check engine light
- Rough idle
- Stalling
How to Fix
Replace the ETM with an updated revision that has improved solder joints. Clear adaptation values after installation. Some shops offer ETM rebuilds at lower cost than new units.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- XeMODeX VO.1020.36001822.00.24-PP pre-programmed contactless ETM
replace a tested failed early ETM with a pre-programmed contactless dual-sensor remanufactured unit Fitment/availability: 2001 Volvo XC70 Turbo using a listed 36001821/36001822/8603652/8644344-family Magneti Marelli ETM; excludes 2002-20…
- XeMODeX VO.1020.30711554H.00.20 contactless electronic throttle body
replace the diagnosed later electronic throttle body after year, engine, original number and wiring checks Fitment/availability: 2002-2004 Volvo XC70 Turbo within the supplier's 2002-2007 application using listed 30711554/30711544/306500…
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Ford Fusion · 2010–2016
The electronic throttle body suffers internal contamination/wear of the motor contacts, causing intermittent electrical failure rather than simple dirt buildup. The result is a sudden loss of power (limp/failsafe mode) with the amber wrench (powertrain) warning light, rough idle, or stalling, sometimes in traffic. Ford acknowledged the problem with extended-warranty program 13N03 for 2010-2013 models and Customer Satisfaction Program 16B32 for certain 2015-2016 vehicles including Fusion.
Common Symptoms
- Wrench/powertrain warning light
- Sudden loss of power / limp mode
- Rough or surging idle
- Stalling
- Reduced throttle response
How to Fix
For the limp-mode failure the throttle body must be replaced (cleaning does not fix internal electronic wear), followed by a mandatory throttle-body relearn to prevent high idle and driveability faults. Check whether the vehicle qualified for 13N03 or 16B32 coverage history.
Sources for this issue (2)
Find P0638 by make
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P0638 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0638 mean?
P0638 stands for "Throttle Actuator Control Range/Performance Bank 1." This code means the engine computer detected that the electronic throttle plate (Bank 1) is not opening or closing to the position it commanded. The PCM monitors throttle actuator position against the desired angle and sets this code when they disagree. This can trigger reduced-power 'limp' mode, hesitation, or unexpected changes in engine response, which makes it a safety-relevant fault.
What are the most common causes of P0638?
The most common causes of P0638 are: Dirty or carbon-clogged throttle body, Faulty throttle actuator motor, Failed throttle position sensor, Corroded or loose throttle body connector, Wiring faults in the throttle control circuit, Mechanical binding of the throttle plate, PCM fault. The specific cause varies by vehicle.
How much does it cost to fix P0638?
Repair costs for P0638 range from $200 to $600, depending on the vehicle and root cause.
Which vehicles are affected by P0638?
Au7o has documented P0638 across 2 vehicle models from 2 manufacturers: Ford, Volvo.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.