TROUBLE CODES - NEED HELP

kowalcs · October 1, 2003

I posted this in the SUV section and am not getting much response. Hopefully some of you guys can help me. My '97 Bravada is spark knocking really bad and bucking and surging all over the place. I rented a code scanner and got the following:

1.) P0101 MAF or VAF CKT Range Perf

2.) P0420 Catalyst Efficiency Below Threshold (Bank 1)

3.) P1406 Manufacturer Controls Aux. Emmissions Controls

4.) P0300 Random/Multiple Cylinder Misfire Detected

What do you guys think? I was leaning towards EGR, but would that cause all of those other codes? Please help if you can.

Thanks.

CMNTMXR81 · October 1, 2003

First things first, what order do they come up as? Reason I ask is 9 times outta 10, you follow that order in troubleshooting.

Your first code P0101 could be the spark causing the other three. Kinda like a domino effect. It may not actually be 4 individual codes that you need to fix.

have you pulled the MAF and checked the resistor grid for damage and or dirt/grime? A simple cleaning MAY do wonders.

kowalcs · October 2, 2003

The codes came up in order as I have them up above. I did take out the MAF sensor last night and cleaned up the resistor grid with a q-tip and some alcohol. The grid looked in good shape, but two of the resistors were pretty black. Do you think that could have caused my problems?

Since you say that the order of the codes means something, does that mean that the MAF sensor is probably the problem? Instead of simply cleaning it, should I replace it? Thanks for your help. I'm kinda surprised that I'm not getting more help from this forum. I get more help from the snowmobile forum I'm on when I ask snowmobile related questions in July.

CMNTMXR81 · October 3, 2003

This forum is a bit down there. I usually only have about 10-15 minutes a day to hit all my car sites. So I don't get down this far often.

Yes, having the senors coated in soot can cause erroneous readings of frequency (in Khz) which determines air speed/velocity as well as volume in (lbs/hr) therefore causing erroneous O2 readings, therefore causing a "catalyt below threshold" etc, etc....

If you had a scan tool on it, did you happen to get the O2 readings in millivolts (mV)? That will tell you whether you're running too lean or rich at idle. .450 is stoich (14.7:1) but sometimes can hover around .485mV and still be stoich. Anything significantly below that is lean, anything significantly above that is rich.

kowalcs · October 3, 2003

I'm not sure if the code scanner I rented has the ability to give specific readings (ie. millivolts at a particular sensor) like you mentioned. I hope to get the thing running on Monday. I'll keep you posted.