My 97 Bravada will not pass the emissions test.They have replaced oxigen sensors , spark plugs, etc. the code for the catalytic will not set to read ready , the mechanic says all it needs is to run it and run it, we have done so and they have done it too, but still does not set it. any ideas? Also one of the fuses gets very hot . Thanks . Ann

Did the tester not tell you why it failed? I would think no muffler would be sufficient cause.

Did you scan for codes to see if there were any besides the catalytic convertor? Unless she's running leaded gas it shouldn't have to be replaced yearly. Is she using an additive that puts lead into the system? I would also check the wire hareness for the O2 sensors. It's not unusual for them to wear and rub a bare spot in the insulation. This will case a short and give a false reading to the computer. Is there any chance that there is a leak in the exhaust? If air is getting in at a joint or a small pinhole ti will screw up the O2 sensor readings.
Hope this helps.

The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
There is an exhaust leak

Sometimes simply resetting the code is all you need to do. Many codes will reset themselves over time. What the person meant was that in normal driving the code may reset itself. You don't need to waste your time or fuel driving nowhere to attempt to reset the code.

Personally, here is what I would do if I were you. If the place in Texas where you are moving to does not require emissions testing, do nothing for now. If the car seems to be running normally the code may reset itself. If Texas requires emissions testing you will need to have the problem addressed or the car will not pass emissions. Bring the car to a reputable independent mechanic for repairs. If it is your catylitic converter expect some sticker shock as these can be expensive. Hope this helps, Please rate this!!! :) James Booth

A Chilton/Haynes manual for your vehicle has the codes. Will also give other ideas on cause for non-passage of emissions. It could be as simple as a good tune-up (new plugs, wires, etc), or as spendy as new catalytic converter.

Did you install new spark plugs? Definitely replace the O2 sensor.

This code is set when the catalytic converters are operating below tolerable efficiency limits. Basically, your catalytic converters are bad and are in need of replacement. You can have bad converters and still pass emissions, but your computer uses the oxygen sensors to determine how well they are working. If the readings are out of a set tolerance, the check engine light will illuminate and DTC P0420 will set. Clearing the code will turn the light out temporarily, but the next time the test is run, the light will come on again.
Hope this helps.

Yes it can be determined by the DTC (Data Trouble code). If the DTC is P0420 (catalyst system efficiency below threshold Bank-1) then the side of the engine with the #1 spark plug and cylinder is always Bank-1, and the O2 sensor that monitors the catalyst efficiency is usually after or (post) of the catalytic converter.

The #1 cylinder is located at the front spark plug on the right or the passenger side of the vehicle, so Bank-1 is on the right side of the vehicle, and the O2 sensor that monitors the catalyst efficiency should be located after or (post) of the catalytic converter. It would be the post right O2 sensor.

There is also the possibility that the catalytic converter is actually starting to fail, and if changing the O2 sensor and clearing the DTC does not solve the problem them the catalytic converter is most likely faulty.

replace the coolant sensor. go to a parts store and ask for emissions test formula. its about $8 a bottle. this should help it pass the emissions test.

Hi.. On your question the definition of the codes are:
P0171, System to lean ( Fuel trim)
P1130, Air / Fuel sensor circuit range ? performance malfuntion This code is exclusive california Emissions). Oxigen sensor Performance malfuntion.
The first step you need to do is Check the Oxigen ( O2 sensor)
Connections The front and the rear one.
Check the condition of the Air filter Replace if need.
Check Spark plug Replace if need.
Check Fuel condition, Replace fuel filter if need.
And Clear the Codes if averything is good.
If the code P1130 return Replace the Air fuel ratio sensor..

Ok.. I hope this help on your question. If need more info letme know.

Thankyou for use fixya...

it means that if u have a catalytic converter then ur catalytic converter which reduce the emissions is not working in proper manner which it means that it is broken