Powertrain, generic (extended)

P239B Diesel Intake Air Flow B Control Motor Current Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

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

Symptoms

  • MIL on
  • Flap switched off and resting at spring position
  • Often stored together with P2391 or the stuck codes

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–600
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

diesel intake throttle valvethrottle valve motoractuator wiring

Related codes

P2390P2392P2393P2391P02EB

References: law.cornell.edu, gsi.ext.gm.com, ms-motorservice.com.