Hello to all! I humbly come before you again!
Here goes: Check engine light came on the second day I went from former sea level home to new residence at 6000 feet! I am unable to rest it, and will need the light to go off to pass smog here in new state. Can you help? I got code 2-4-1, 1991 740 178,000 miles! No outward signs of increased temp or decreased performance!

How many start/stop cycles have you gone through at your new altitude?

It is possible that your car will compensate for the new conditions if you cannot find any problem.

Try not to throw parts at it.

Have you checked the FAQ?

Sorry, but where do I find the FAQ's?
Went through many numerous cycles.
I couldn't erase the code, but disconnected the battery and light went off for a tank of gas driving daily running errands.
Yesterday filled up tank, drove 50 miles. Today CEL back on again.
I will check vacuum leaks at EGR switch/solenoid, and maybe pull it out. Will check the EGR sensor also! Thanks to everyone again! Bone...

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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How are you doing Kitty!

I agree. With a 27 year old car a clogged EGR valve or piping is a good bet. Seen that happen on 850’s. Might be able to use a drill or similar to clean them out w/o buying new parts. This problem often doesn’t affect the car’s running but will throw a CEL. Since it is emissions related that will cause an emissions failure when the car is inspected. This is assuming that Rattlebone54’s new state performs emission inspections...

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Will I buy another Volvo??? We'll see....

Hiya Mr. Walker!!!!

Happy Sat-Your-Day (all day long)!!!!

I used a section of dowel with a point carved out at the end and twist it in to dig the exhaust gas condensate out. Yet the big egr pipe where it connects at the exhaust manifold can break and rust there.

Unless the vacuum control is futzed or the temperature sensor.

How am I doing? Rather awful. Now. No more cGMP.

Hope you and yours are well.

I guess Rattlebone54 did not find my posts helpful?

Happy Sat-Your-Day. Or Caturday. Or Dogurday.
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Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.

Which FI system does your 740 have?

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Will I buy another Volvo??? We'll see....

Not regina jwalker! Thanx-Rattlebone

Evidently not Bosch LH 2.4 as there is no code 241. Had LH 2.4 in my 90 240. Is it Bosch Mototronic? If so, code 241 is an EGR code. Which will trigger a CEL and yet might not affect engine performance. Check the 700/900 FAQ on this site for more info.
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Will I buy another Volvo??? We'll see....

Hiya Mr. Walker!

Happy Sat-Your-Day (all day long!)

The fault code for 1991 740 with (normally aspirated - not turbo, yes? Bosch engine control is socket six on the OBD-1 code reader with the red blinky LED.

So, the EGR is monitored and controlled by the EZK ignition computer. That is socket two on the OBD-1 reader.

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

No Motronic. No sensor on your EGR Valve.

Socket two is fuel injection.

Socket six fault code 2-4-1 EGR system flow too low.

Sets a CHECK ENGINE dash light.

Meaning the EGR temperature sensor, at the vacuum controlled EGR valve or downstream, is encountering conditions outside the range engine control is set to encounter for the running condition.

The fault code may (or reads as) the EGR piping is somehow clogged. Engine combustion vapor in the exhaust condensate usually collects at the EGR pipe union with the air intake port manifold.

The EGR valve may not be opening or opening as it should. Also, the EGR vacuum solenoid may not be working. Machine Man Phil makes mention in his post of a foam material under the vent cap that deteriorates. Phil says he removes what remains of the foam material, and replaces with a mesh or something that can serve as a sort of air filter in that application.



https://www.eeuroparts.com/Parts/7729/EGR-Vacuum-Solenoid-3531138/

A vacuum leak of an EGR system vacuum line where it connects at the solenoid or the EGR valve.

As you diagnose, take a look at the EGR pipe that secures at the back of the exhaust manifold and the other end at the EGR valve. The (EGR exhaust vapor piping is made of) stainless fails, the pipe form a leak or worse.

Or the EGR temp sensor may be failing? Usually the thin curly black wiring wiring fails at the sensor. The copper conduct breaks - fatigue from vibration or flexing all them years. The sensors are fragile yet last a long time.

Hope that helps. Questions?

Thank you.

Buttermilk Boy with loaves of savory ultra sourdough bread.

With buckets of earl grey tea.





Is this really true?








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2-4-1 indicates a fault in the EGR system

So according to this site's 700/900 FAQ (Thank you Steve Ringlee!!) if it's not a Regina then the only other system with EGR is the Motronic 1.8.

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

According to the fault table, the problem is "EGR system flow too low". It also gives a possible cause being the "EGR vacuum booster".

Good luck!