I'm getting a check engine light along with the brake and battery light on my 2000 rodeo v6 auto. The codes are 0171,0172,0174,0175(lean,rich,right,left) or some variation. If I keep driving after about ten minutes it starts acting like the alternator has gone out(dim lights, no power, transmission acts funny). If I reset the codes everythig goes back to normal, until the next time. I've tried searching the forum but haven't found anything that addresses this exact problem, or I missed it. If I don't find an answer I'm going to have to take it to a dealer (shudder) so any input is appreciated.

The twinkling of the dash lights usually indicates an impending demise of the alternator. Start there.

Michael

This has been going on for a few months. The first thing I did was to change the alternator. I'd forgotten until you mentioned it. The only other things I've done are spark plugs and injection cleaner(marvel). The problem remains. It runs fine until the cel brake and batt lights come on then everything changes. I keep the scanner in my glove box. When the dash lights come on I plug in the scanner and wait for the codes to clear. Once they're clear the truck runs fine.

Next time the codes come on, clear them with the scanner and then disconnect the battery for about 1/2 hour... sometimes the ECU needs to be reset to clear its "memory" from the codes.

HTH
Van <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />

The codes you list should not be causing the light problem. I would be inclined to suggest you have a bum alternator which is intermittently acting up.

Other than that, I believe those codes are related to the O2 sensors.

Good Luck,
Michael

as much as it seems those codes would by caused by o2 sensors they are almost never actually caused by faulty o2s. lean and rich codes are actually pretty difficult to diagnose properly because you need to be able to datalog what all the sensors are showing to the ecu.

being a drivability tech on fords for 8 years ive seen maf sensors cause both lean and rich but not very often.

next time it starts to run poorly go unplug the maf sensor. if it starts up and runs ok thats possibly your problem.


the battery light is likely another concern alltogether. check voltage next time it happens. if you put a reman alternator on i wouldnt trust it.

Actually, you are right. I was thinking of something else (or just something entirely wrong), but I am now leaning towards looking at the intake manifold gasket. I would bet dollars to doughnuts you have a cracked gasket. The lean/rich and left/right codes are well associated with gasket failures.

Spray some carb cleaner or starting fluid around the intake with it idling. It will rev a bit when you find the hole.

Good Luck,
Michael

yup. intake leaks are the most common reason i see here at work for 0171/0174 codes. i almost never see the rich codes though.

Sounds like an intake manifold gasket OR a throttle position sensor, I've seen both throw the codes you are talking about. Usually an intake manifold leak will cause some issues that do not go away. Spray some engine cleaner around the intake manifold gasket, it made a loud sucking noise when I hit the leak on my 2001 Rodeo.

Does it run smooth after you clear the CEL? No hiccups from the engine? The TPS connected to the accelerator pedal could be the culprit, it was on my daughter's Rodeo. Any pedal assembly from a 2000-2004 should work. I replaced my daughter's 2000 Rodeo's with one from a 2003 Axiom, no problems since.