P2084Powertrain
Powertrain · SAE
Exhaust Gas Temp Sensor EGT B1S2 — Performance
Meaning
The exhaust gas temperature (EGT) sensor on bank 1, position 2 (downstream, typically after the diesel oxidation catalyst or between the DOC and DPF, or after the DPF) delivers a signal within the permitted range but the value does not match the ECU's expectations. This is a rationality fault.
Common causes
- Aged or partially failed EGT sensor B1S2 with calibration drift
- Exhaust gas leaks upstream of the sensor altering the reading
- Soot or ash deposits on the sensor degrading thermal response
- Actual gas temperature too high or low relative to the map (abnormal regeneration or blocked DPF)
- Discrepancy between EGT S1 and EGT S2 detected by the ECU as an anomaly
Symptoms
- Check engine light on
- Downstream EGT data plausible but inconsistent with expected temperature difference between S1 and S2
- Possible incorrect DPF and regeneration management
- Undetected DPF overtemperature risk
- Related EGT codes possible (P2080, P2458, P2463)
Severity
Moderate: an incorrect downstream EGT sensor reading compromises DPF and regeneration management; over time this can cause thermal damage or reduced effectiveness of the exhaust aftertreatment system.
What to do
- Check EGT sensor B1S2 live data with scan tool and compare with EGT B1S1 (the difference must be consistent with sensor positions)
- Physically inspect the sensor for corrosion, deposits, or mechanical damage
- Check the exhaust system between the DOC and DPF for gas leaks
- Perform a DPF regeneration while monitoring both EGT temperatures for consistency
- Replace the EGT sensor B1S2 if out of calibration despite intact wiring