Oldsmobile/Buick Repair/volt light

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Question
Hi Tom,

The work never ends. There are two issues I am working on...
1) I keep getting code p0171 for lean bank 1, already replaced both Ho2 sensors(bank 1 has AC Delco sensor), cleaned mass air with electrical spray, checked vacuum lines-nothing obvious, cleaned pcv valve, installed new fuel filter. Car runs well, no overheating or coolant leaks, no lope in idle. Just the same code coming back not long after startup and I need to clear it to pass.

2) As i pulled up to shed to look some more for the above, car instrument gauges went wacky then dead. Shut car off, wouldn't start again. Jumped it, checked alt with volt gauge(8), alt bad. Replaced with another alt and rechecked, great volts between 13.6 and 14.4, charging as it should. Car looks good, dash fine, runs well, then after a few seconds the volt light comes on on left dash. Now, my dash has the readouts and selections I can go through such as oil life, fuel mileage, air tires, and volts. I had it on volts, while car running and it was reading normal, all the while the volts light is on. At this point I'm scratching my head, as the car is fine, but the light troubles me. I go through my Haynes and try to diagnose. I unhook neg bat cable, run test light between cable and battery, still lit. I unplug the main wiring harness on alt while test light in between bat and cable, still lit. I go through all the fuses in the underhood box with the same and in the last row is a large fuse (bat 1) 30 or 40amp, that when I unplugged it, the test light dimmed. It didn't go out, just dimmed half and when I reinserted it, it lit the test light back normal. What does that mean, if anything? Could that be related to the volt light? And lastly, since the car is running/charging normally, should I just ignore that light?

Thanks for reading this lengthy description.

Answer
HI MIKE,,WELL LETS START WITH QUEST# 1 I WILL ASSUME THIS IS A V6 YES...YOU HAVE CHECKED ALL THE IMPORTANT THINGS FOR AS A LEAN CODE..THIS IS GOOD.. DID YOU TRY AND SPRAY ANY CARB CLEANER AROUND THE BASE OF THE THROTTLE BODY AND INTAKE AREA TO MAKE SURE THERE ARE NO VACUUM LEAKS ??? IF SO I WOULD LIKE YOU TO DO SINCE I AM NOT AT WORK TO CK A WIRING DIAGRAM IS TO GET YOUR DVOM AND CK FOR VOLTAGE ON THIS HARNESS TO THE O2 SENSOR AND THEN COMPARE THE READINGS TO THE BANK 2 SENSOR WHILE THE ENG IS RUNNING, IF V6....SHOULD BE THE SAME.1 WIRE SHOULD HAVE 12  PLUS VOLTS AND THE OTHER A REFERENCE SIGNAL FROM THE PCM LIKE 5 VOLTS OR SO...I THINK YOU MAY HAVE BREAK IN THE HARNESS SOMEWHERE...LET ME KNOW WHAT YOU FIND..

QUEST #2 WITHOUT LOOKING AT A WIRING DIAGRAM I CAN NOT ANSWER THE DIM TEST LIGHT WHEN YOU REMOVE THE FUSE..ONE WOULD THINK IT IS CUTTING VOLTAGE TO THIS CIRCUIT. BUT I DO NOT FEEL THIS IS A WIRING PROBLEM..THIS SOUNDS TO ME LIKE THE REBUILT ALTERNATOR HAS A BAD DOIDE TRIO..IT MAY CHARGE TO VOLTAGE SPECS BUT IS NOT CHARGING THE WAY THE DASH LIGHT WANTS TO SEE IT.UNDER SPEC.IF YOU HAD AWAY OF LOADING DOWN THE SYSTEM TO CK FOR AMPS OR RIPPLE EFFECT[CARBON PILE] WITH THE VOLTAGE YOU MAY SEE THE PROBLEM. BEFORE YOU TEAR YOUR HEAR OUT, IF THIS LIGHT WAS OK BEFORE THE REBUILT ALTERNATOR WENT IN,,??? I WOULD GET ANOTHER ALTERNATOR INSTALL IT AND SEE WHAT HAPPENS.
ALL THE LIGHT ON THE DASH DOES IS EXCITE THE ALTERNATOR WINDINGS TO TELL IT TO START CHARGING OUTPUT AND TO OF COURSE NOTIFY YOU IF IT IS NOT CHARGING..SO IF NO LIGHT WHEN KEY IS TURNED ON ALT WILL NOT START UP CHARGING.....LET ME KNOW WHAT YOU FIND..GOOD LUCK,,,TOM.

HI AGAIN MIKE,,I STILL THINK YOU SHOULD TAKE THE REBUILT ALT BACK TO THE STORE. THEY ARE JUST LOOKING AT OUTPUT VOLTAGE AND MAYBE AMPS,EACH TESTER IS DIFFERENT..SOME MACHINES WILL NOT TEST FOR DIODE PROBLEMS.[RIPPLE TEST]. IF THIS LIGHT ON THE DASH WAS OUT BEFORE YOU HAD THIS PROBLEM MY MONEY IS ON THE REBUILT ALT OR THE FIELD PLUG THAT PLUGS INTO THE ALT..TRY WIGGLING THIS AROUND WHEN IT IS UP AND RUNNING,SEE IF THE LIGHT GOES OUT. I HAVE SEEN SOME POOR CONNECTIONS AT THIS PLUG...LET ME KNOW HOW IT GOES...TOM..

Oldsmobile/Buick Repair

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TOM SHEETS

Expertise

Can answer all questions pertaining to mechanics of GM cars from 1965 to present. I will answer questions from 6:00 am to 10 pm est.. I will not take diesel or paint questions. If this olds and buick section is maxed out you can get to me in the chevrolet section...

Experience

I have 30 plus years experience in servicing these cars. I can answer questions on carburetor, fuel injection,ignition systems, suspension, brakes and abs, cooling systems,a/c and heater,manual transmissions, rear differential and electrical system,charing system and battery. I am a Master ASE certified mechanic in all 8 categories: - Brakes - Heating and Air Conditioning - Automatic transmission - Clutches and Transaxle - Engine performance - Engine repair - Electrical - Steering and suspension I am certified for NYS inspection and clean air insp.

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Education/Credentials
I am a Master ASE certified mechanic in all 8 categories (see above) I am an Air Conditioning/Freon recycling specialist with ASE. I have at least 4 years of technical training and many hours of continuing education.

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many customers in our busy shop for the past 30 plus years

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