Hi,
I bought a 2002 Montero Limited few days ago and the 'Service Engine Soon' light was on. So I got the codes from an Autozone. There were 9 codes total, but he said some of them were duplicates.
This is what I got.
P0134 - Cylinder 1-4 heated oxygen (front) sensor no activity detected
P0340 - Camshaft position sensor (CMP) circuit
P0401 - EGR insufficient flow detected
P0403 - Exhaust gas recirculation (EGR) control circuit
P0431 - Warm up catalyst efficiency below threshold - cylinders 2-3

What could be the reason behind all of these codes? Is it like a single sensor or one part causing multiple codes?
Any help appreciated.
Thanks in advance.

PS : This is my secondary moving things/ snow days backup vehicle. So I'm not worried about things like fuel efficiency. Just wanted to make sure that it won't break down in the middle of the road.

 

Check your ECU. Remove your ECU, yank off the cover, and look for damage.

When it spits out that many codes, it usually means it's toast.

 

Thanks for the reply.
So you mean there would be visible burn marks on the unit?
Now I'll have to find a youtube video to see where the ECU is located

 

Here ya go: http://www.justanswer.com/mercury/3a...ero-sport.html

And yes, you will either see burn marks or on the reverse side, you will see where the pins have been soldered on they are a different color than the rest. This means heat, and heat is bad in electrical components.

 

Thanks.

 

I know its a old post but was that really your ECU or the CAT causing all of these codes ?

 

Those codes are for different circuits and it is likely that all the codes were true. Since there is a "no activity" code and "circuit fault" code, I'd guess it can be a damage to a wiring harness. It would be nice if OP could reply what the solution was.

 

The engine became as loud as a tractor, so I had the Camshaft position sensor, timing belt, serpentine belt, plugs/wires changed, and that was fixed. The light was still on. Given the price of the vehicle I didn't want to invest too much money in it, so never bothered to really look into the lights. I used it in the same condition for another 3 years and sold it off.
Sorry I can't be anymore of help to you :-)
Good Luck!

 

no worries. Thank you for your input & time.