No signal at diagnostic terminal

[jdrh]

I purchased a 98 Venture that runs great, but the service engine light and air bag lights are on all the time. I purchased an OBD2 code reader, but can't get a signal at the diagnostic terminal. I've tried the code reader on other GM products and it works fine. Where do I start looking for the problem?

[AOneill]

check your fuses on the right hand passenger side panel, you will find a 10a fuse running cigar/DCL(diagnostic link conector) hope this is the fix to your problem

[jdrh]

Thanks for the tip. The fuse was burned out because the cigar lighter was shorted. Code reader now gets a signal. The code reader came up with two generic codes, cylinder 4 misfire detected and catalyst system efficiency below threshold (Bank 1)
If anyone knows anything about these, I will be glad for any info. Meanwhile I will search the internet.

[500horses]

I just replaced the secondary O2 sensor after getting codes PO 140, 300, 401.(same as or similar to your readings) after driving the car a few times, the light went out.

[maxwedge]

Fix the misfire problem you may loose the cat efficiency code.

[GMMerlin]

Originally Posted by maxwedge

Fix the misfire problem you may loose the cat efficiency code.

Probally not..if this code is displayed, the converter needs to be replaced.
But the misfire needs to be corrected, because a misfire will kill a converter

[jdrh]

I cleared the codes and the only one that came back was P0420.
My next step will be to test the O2 sensor after the coverter. I imagine the catalytic converter is kinda pricey. Thanks for the help.

[cdru]

Originally Posted by jdrh

I cleared the codes and the only one that came back was P0420.
My next step will be to test the O2 sensor after the coverter. I imagine the catalytic converter is kinda pricey. Thanks for the help.

Universal cats can be had for around $60. If you don't have any performace upgrades it likely will be more then sufficient. I replaced one in my minivan recently. I purchased it at a parts store and took it to a muffler shop to weld in for $50. I could have done it my self with clamps but it was 15 minutes of their time or an hour or two of my time... I went the better quality route and paid the $50.