Faulty exhaust aftertreatment glow plug (open or shorted element); Damaged or corroded wiring or connector at the glow plug; Blown fuse or faulty relay supplying power to the glow plug circuit; Failed glow plug control module or driver circuit in the engine control module; Exhaust system modifications or leaks affecting glow plug operation; Software calibration issue requiring an update (less common)

DTC codes / P26xx · Computer and output circuits / P26A0

P26A0Exhaust Aftertreatment Glow Plug Performance

Q: What does code P26A0 mean?

Exhaust Aftertreatment Glow Plug Performance. P26A0 indicates that the engine control module has detected a performance issue with the exhaust aftertreatment glow plug, which is used to heat the exhaust system and help reduce emissions during cold starts. The computer monitors the glow plug's electrical circuit and expects a certain current draw or temperature rise when commanded on, and it sets this code when the actual response falls outside the expected range.

P26A0 indicates that the engine control module has detected a performance issue with the exhaust aftertreatment glow plug, which is used to heat the exhaust system and help reduce emissions during cold starts. The computer monitors the glow plug's electrical circuit and expects a certain current draw or temperature rise when commanded on, and it sets this code when the actual response falls outside the expected range.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Extended crank time or rough running during cold starts if the glow plug is not heating properly
Increased exhaust smoke or odor during cold engine operation
Reduced fuel economy or power in some cases due to altered regeneration strategies
Possible limp mode or reduced engine performance if the fault escalates

Common causes, most likely first

Faulty exhaust aftertreatment glow plug (open or shorted element)
Damaged or corroded wiring or connector at the glow plug
Blown fuse or faulty relay supplying power to the glow plug circuit
Failed glow plug control module or driver circuit in the engine control module
Exhaust system modifications or leaks affecting glow plug operation
Software calibration issue requiring an update (less common)

How to diagnose and fix it

Scan all modules for stored codes and freeze frame data to confirm P26A0 is the primary fault
Visually inspect the glow plug, wiring, and connectors for damage, corrosion, or loose connections
Check the glow plug circuit fuse and relay, and test for power and ground at the glow plug connector
Measure the resistance of the glow plug and compare to the manufacturer's specification
Command the glow plug on with a scan tool and verify current draw or temperature change
If the circuit and glow plug test good, diagnose the control module or wiring back to the engine control module
Replace the faulty component and clear codes, then verify the repair with a test drive and monitor readiness

Glow Plug Circuit Checks Before Replacement

A common mistake is replacing the glow plug without checking the control module or wiring, which can lead to repeat failures if the root cause is a damaged harness.
The exhaust aftertreatment glow plug is often confused with the engine glow plugs, but it serves a different purpose and is located in the exhaust system, so misdiagnosis can occur.
Some vehicles use the glow plug for exhaust system heating during regeneration; a fault may not trigger a noticeable symptom until regeneration is inhibited, leading to clogged filters.
Resistance testing alone can be misleading because the glow plug may test good at room temperature but fail when hot; a current ramp test with a lab scope is more reliable.
After repairs, a relearn or adaptation reset may be required for the new glow plug to be recognized by the control module.

Can I keep driving with P26A0?

You can generally continue driving with this code, but avoid long periods of idling and schedule a diagnosis soon to prevent potential exhaust aftertreatment issues. If the check engine light starts flashing or you notice severe power loss, stop driving and seek professional help.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.