OBD-II code · Powertrain (generic, extended)
P2491 EGR Cooler Bypass Control Circuit High Bank 2
Same as P245D on bank 2. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.
Is it safe to drive with P2491?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyControl line shorted to supply
- Less likelyConnector pins corroded - high contact resistance
- Less likelySupply wire pinched against B+ source
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 1–3 h
- Emissions test
- Likely to fail
- Parts involved
- Egr Cooler Bypass Valve B2
Related codes
- P245DEGR Cooler Bypass Control Circuit High Bank 1
- P248EEGR Cooler Bypass Control Circuit Open Bank 2
- P248FEGR Cooler Bypass Control Circuit Range or Performance Bank 2
- P2490EGR Cooler Bypass Control Circuit Low Bank 2
- P2492EGR Cooler Bypass Position Sensor Circuit Bank 1
- P2493EGR Cooler Bypass Position Sensor Range or Performance Bank 1
- P2494EGR Cooler Bypass Position Sensor Circuit Low Bank 1
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.