P239B checks the current the B-throttle motor draws while its H-bridge is switched on. A blocked or very stiff flap, a partly shorted winding or the two motor leads touching each other push the current beyond what the module expects. No manufacturer publishes P239B with values. GM's 2017 diesels set the A-motor code P02EB once more than 5.5 A is seen in 160 out of 200 evaluations while the powertrain relay delivers over 11 V; the MIL follows on the second trip. What sets it apart from P2393 is the origin of the excess current: here it comes from the load itself rather than from a lead touching battery voltage. Checking whether the flap moves freely, with the unit removed if necessary, shows whether it binds. Once the driver shuts down, the spring opens the flap; the engine keeps running with restricted EGR control.
Medium severity. Can I keep driving?You can drive in moderation. Get it repaired soon, because a loose flap can cause major damage on some engines.
Symptoms
- MIL on
- Flap switched off and resting at spring position
- Often stored together with P2391 or the stuck codes
Most likely causes
- Flap blocked or very stiff, motor running at stall current
- Partly shorted motor winding
- Short between the two motor leads in harness or connector
- Faulty current measurement in the control module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P239B means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 3: Ignition and misfires
- 9B: Specific fault in that system
Frequently asked questions
Can I keep driving with code P239B?
You can drive in moderation. Get it repaired soon, because a loose flap can cause major damage on some engines.
What causes code P239B?
The most common causes are: flap blocked or very stiff, motor running at stall current; partly shorted motor winding; short between the two motor leads in harness or connector.
Related codes
- P2390Diesel Intake Air Flow B Control Circuit/Open
- P2392Diesel Intake Air Flow B Control Circuit Low
- P2393Diesel Intake Air Flow B Control Circuit High
- P2391Diesel Intake Air Flow B Control Performance
- P02EBDiesel Intake Air Flow A Control Motor Current Range/Performance
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 17OBDG04 Engine Diagnostics
- ms-motorservice.com: throttle valves and regulating throttles
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.