01 Why Mechanics Don’t Always Show You the Real Fault • 02 How to Start an Automotive Business With Almost No Capital • 03 What Causes the Check Engine Light to Come On? • 04 The Common Mistake Nearly Half of Drivers Are Making Withou… • 05 People Cannot Believe The Secret Function Of The Small Arro… • 06 How A Simple Mistake At The Gas Pump Could Destroy Your Eng… • 07 P0116 – Engine Coolant Temperature Range Fault: Causes and … • 08 Why The Traction Control Light Comes On During Normal Drivi… • 09 This Is Why The Air Recirculation Button Is So Important • 10 Why Your Car Revs High But Doesn’t Go Fast •

DTC codes / P26xx · Computer and output circuits / P26A2

P26A2Exhaust Aftertreatment Glow Plug Circuit High

P26A2 indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the exhaust aftertreatment glow plug circuit, which is used to heat the exhaust system for emissions control. The PCM monitors the circuit and sets this code when the voltage exceeds the expected range, typically indicating an open circuit, high resistance, or a faulty glow plug.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp).
  • Often no symptoms besides the warning light.
  • Possible reduced fuel economy or performance if the glow plug is needed for regeneration.
  • In some cases, a noticeable delay in exhaust aftertreatment system readiness.
  • Rarely, a burning smell or visible damage to the glow plug wiring.
  • No noticeable drivability issues in most cases.

Common causes, most likely first

  1. Open or high-resistance wiring in the glow plug circuit (e.g., broken wire, corroded connector).
  2. Faulty exhaust aftertreatment glow plug (internal open circuit).
  3. Poor electrical connection at the glow plug or control module.
  4. Failed glow plug control module or relay.
  5. PCM internal fault (rare).
  6. Short to voltage in the glow plug circuit (less common).
  7. Aftermarket or incorrect glow plug installed.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for related codes.
  2. Inspect the glow plug and its wiring for visible damage, corrosion, or loose connections.
  3. Measure the resistance of the glow plug and compare to specification; replace if out of range.
  4. Check the glow plug control module and relay for proper operation.
  5. Perform a voltage drop test on the circuit to identify high resistance points.
  6. Repair or replace any damaged wiring or connectors.
  7. Clear the code and verify the repair with a test drive.

Don't overlook the glow plug control module

  • A common mistake is replacing the glow plug without checking the control module, which can cause the same code if it fails to provide proper voltage.
  • Corroded connectors at the glow plug are a frequent cause of high voltage readings and are often missed during visual inspection.
  • The code can be set by a short to voltage in the circuit, which may not blow a fuse but will cause high voltage at the glow plug.
  • Always check for technical service bulletins (TSBs) for your specific vehicle, as some models have known issues with the glow plug circuit.
  • After repairs, the glow plug may need to be commanded on with a scan tool to verify proper operation, as it may not activate during normal driving.

Can I keep driving with P26A2?

It is generally safe to continue driving with this code, as it usually does not affect drivability, but avoid long trips or heavy loads until repaired to prevent potential emissions system damage. Have the vehicle diagnosed promptly to ensure the aftertreatment system functions correctly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage