Click FAQ at the top of each brickboard page.

https://www.brickboard.com/FAQ/700-900/

All too little About EGR:

https://www.brickboard.com/FAQ/700-900/EngineSensors.htm#EGRValve

Here is a link direct to the page that explains the OBD on your 1991 Volvo 740 I posted some days ago in this thread of yours:

https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

I also explain the code you have, fault code 2-4-1, is specific to OBD code reader, with blinky-blinky red LED, socket six, and that the fault is with in the exhaust gas recirculation (EGR) emission control system. EGR is too reduce oxides of nitogen, yet eats about a gallon per mile off the fuel economy versus the same year and model Volvo without EGR.

Socket six OBD fault code 2-4-1 means EGR system flow too low. The EGR temperature sensor is encountering a reduce duration or flow of exhaust gas. May also suggest a faulty temp sensor, as the braided copper conductor at the sensor can fatigue and break. Though more likley the EGR piping is clogged or EGR control us faulty.

Resetting codes at the OBD code reader box or by disconnecting a fuse does not cure the fault cause, if the fault causes persists with the fault code setting again and the cluster CHECK ENGINE light illuminating.

The cause of this EGR fault has little to nothing to do with your elevation change.

I used to reside in Novato, CA.

Where did you relocate to at 6000 feet above mean sea level?

cheers,

Thursday Duffed.


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