My car is a 1997 mazda 626 with a 2.0L 4 cylinder engine and will not idle however it runs smooth above 1000 RPM. The diagnostic test shows a P1131 code. I changed the #1 (fwd) O2 sensor. No help. I cleared the code and it still comes back with P1131. Any suggestions?

 

hey dude, one thingwith cars with ECU's is; if you don't know what your doing or how to fix the problem yourself...DONT!! i have a friend who thought he could reset his ECU withouta backup computer and lost everything!!, it was just over $2000 for a new one...you just have to weight it up.</P>


sorry i couldn't be more helpful.</P>


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This code indicates P1131 Lack of Upstream Heated Oxygen Sensor Switch ...You may have replaced the wrong sensor if there is more than one.
There could be many causes for this error though...there are numerous values that could be out of spec enough to cause this....

- short or corrosion in wiring harness
- moisture in harness or connectors
- damaged/defective O2 sensor(s)
- damaged PCM
- excessive fuel pressure
- leaking injectors
- leaking fuel pressure regulator (low fuel pressure)
- car is almost out of fuel
- air leaks after MAF sensor
- vacuum leak
- PCV system clogged or leaking
- engine oil dipstick not seated
- EGR valve gasket leaking
- stuck EGR valve
- leaking diaphram on EVR
- oil overfilled
- cam timing is off
- cylinder compression too low
- exhaust leak near the O2 sensor
- any air or vacuum leak


The previous poster is silly. Automotive computers use ROMs, you can't "reset" or erase them without special equipment, unless you're really careless and short something out.