Cause
Failed control module output driver
The transistor stage inside a control module that switches an actuator has failed. It is the least common explanation for most circuit codes and should be the last conclusion, not the first — the wiring and the actuator are both far more likely and both far cheaper.
But the reason it matters is what usually kills it. These drivers switch inductive loads — injectors, solenoids, relays, heaters — and every switch dumps the collapsing magnetic field back into the driver. They run hot and stressed by design. When one fails, the common cause is a short in the load it was driving: a shorted injector, a glow plug that has failed short, a solenoid with a broken-down winding.
Which is the practical point: measure the actuator before replacing the module. A new module fitted into the same short destroys its driver too, and that is an expensive way to learn what the meter would have shown in a minute.
Failures are usually one output at a time rather than the whole module, so the pattern is faults on one or two circuits while everything else works normally. Expect a replacement module to need programming and coding, and on some vehicles to hold calibration data that must be transferred with it.
Typically specialist work. Needs equipment or training most home workshops do not have.
Some of these codes mean you should stop driving
2 of the 11 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (11)
Codes where this is a likely explanation first, rather than merely a possible one.
- P05F8 Reductant Heater Control Module Performance Moderate
- P062B Internal Control Module Fuel Injector Control Performance High
- P084F Park/Neutral Switch Output Circuit Moderate
- P263E Glow Plug Control Module 1 Over Temperature Moderate
- P2AF5 Starter Relay C Stuck On High
- P023B Charge Air Cooler Coolant Pump A Control Circuit Low Moderate
- P06DE Engine Oil Pressure Control Circuit Stuck On Moderate
- P20CF Exhaust Aftertreatment Fuel Injector A Stuck Open Stop driving Critical
- P20DB Exhaust Aftertreatment Fuel Supply Control Stuck Open Stop driving Critical
- P20F6 Reductant Injection Valve Stuck Open Bank 1 Unit 1 High
- P24B5 Particulate Matter Sensor Heater Control Circuit Low Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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