What P0639 means
P0639 is the bank 2 counterpart of P0638 and only applies to engines with two separate electronic throttles, one per cylinder bank (some V8, V10 and V12 engines with separate intake paths).
How the engine computer detects it
The module compares target and actual angle and the duty cycle the motor needs; if the plate does not follow, it is de-energized and springs to its rest position, and power is limited. No manufacturer document available to us uses P0639 – this follows P0638 (Subaru: more than 3.5° deviation for 250 ms) and CARB's function check of output components. Ford calls a second throttle 'throttle actuator B' and reports it as P211A ff, its sensors as sensor C (P0225/P0229). Uneven filling of the two banks can also cause a rough idle.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light
- Limp mode, loss of power
- Rough idle from uneven bank filling
Common causes
- Bank 2 throttle dirty or stiff Most likely
- Bank 2 actuator motor or gears faulty Possible
- Icing Less likely
- Wiring or module Less likely
How to diagnose P0639
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: throttle body, throttle actuator motor, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 6
- Computer and output circuits
- 39
- Specific fault
Questions drivers ask
Can I drive with code P0639?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0639?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Can I fix P0639 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.