P20E4 covers the pair around the particulate filter: sensor 2 at the filter inlet and sensor 3 at its outlet on bank 1 no longer agree. GM documents the code for the diesel in table 15OBDG04 (also 14OBDG04): after a soak of at least 28,800 s the start-up values of the filter upstream and downstream sensors are compared against a look-up limit, and a larger gap is a Type B fault. Because both sensors steer and protect filter regeneration, a biased one can lead to regenerations that run too cool or too hot. P20E2 covers the pair around the oxidation catalyst, while P2084 and P242B report range faults of a single sensor. The patent US7533519 uses the same inlet/outlet arrangement for its stuck-in-range test. Drivers usually see the MIL and may notice more frequent or aborted regenerations.
Medium severity. Can I keep driving?If the light is on steadily, take a highway drive or go to a repair shop soon. If the car is in limp mode or the light is flashing, do not push the engine.
Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.
Symptoms
- Malfunction indicator lamp on
- Regenerations aborted or happening more often
- Filter loading warning in some vehicles
Most likely causes
- Filter inlet or outlet temperature sensor aged by heat cycling
- Heat-damaged or corroded sensor connector or lead
- Heavy soot or ash deposits on a sensor tip slowing its response
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P20E4 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 0: Subsystem depends on the code range
- E4: Specific fault in that system
Frequently asked questions
Can I keep driving with code P20E4?
If the light is on steadily, take a highway drive or go to a repair shop soon. If the car is in limp mode or the light is flashing, do not push the engine.
What causes code P20E4?
The most common causes are: filter inlet or outlet temperature sensor aged by heat cycling; heat-damaged or corroded sensor connector or lead; heavy soot or ash deposits on a sensor tip slowing its response.
Related codes
- P20E2Exhaust Gas Temperature Sensor 1/2 Correlation (Bank 1)
- P20E3Exhaust Gas Temperature Sensor 1/3 Correlation (Bank 1)
- P2084Exhaust Gas Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 2)
- P242BExhaust Gas Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 3)
- P2031Exhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 2)
- P242AExhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 3)
Sources
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.