Bonne acting strange - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-14-2011, 02:16 PM   #11
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The DTC/voltage problem I described in this thread seems to imply a connection between the PCM and the alternator. According to the factory shop manual, there are two wires connecting the PCM to the alternator (L and F terminals). It'* my understanding that one or both wires provide current to the rotor, which would mean that if there were any connection faults, the alternator output would be adversely affected. Any thoughts?
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Old 04-15-2011, 07:14 AM   #12
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According to the factory shop manual, there should be 4-14V at the alternator connector L terminal with the ignition switch in the RUN position. I got a reading of 28mV. I did get 5V with the engine at idle. I checked the continuity of the red wire from terminal L to terminal 61 on the PCM C2 (clear) connector and it was OK. The manual goes on to say that if the L terminal voltage is out of spec and continuity is good to replace the PCM. Considering this and the fact that the voltage randomly drops from approx 14V to 12V, it does sound like the PCM is experiencing intermittent failure. Is there anything else I should check before replacing the PCM?
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Old 04-18-2011, 08:11 AM   #13
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More symptoms. I was parked in my driveway, stationary with the trans in park with a normal idle and normal voltmeter reading when I blipped the throttle. Instead of returning to the normal readings, the idle speed dropped below 500 RPM (on the dash tach), the lights dimmed, and the voltmeter reading was just above the lower red zone. After a few seconds, everything returned to normal. I was able to reliably get this behavior several times. I pulled the car in the garage (moving the car a distance of 20 ft) to investigate further and the symptoms disappeared. I could not get the car to act up again.

Your suggestions as to what to check next would be appreciated, as if at all possible, I do not want to resort to indiscriminately replacing parts.
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Old 05-09-2011, 08:05 AM   #14
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My idle/voltage problem was caused by a faulty mass airflow (MAF) sensor. As I mentioned in an earlier posting in this thread, the MAF sensor was replaced with a used unit, but this one failed as well a few weeks after installation.

Based on what I've read in this and other forums, the PCM cuts off the alternator field current below a certain engine RPM. The idle speed, at times, was low/unstable to begin with due to the defective MAF sensor, and turning the wheel caused a further drop in rpm due to the drag of the pump, resulting in low alternator output voltage.

Based on my experience in solving this problem, I would strongly recommend the purchase of a good scan tool, specifically one that can record real-time data values. Due to the voltage problem, I assumed (I know, I know) that this was causing the P0102 code to set and the unstable idle when it was actually the reverse. When I first recorded the MAF sensor frequency, it was normal, but then I noticed the reading intermittently dropping to zero, which I probably would not have found if it weren't for the recording ability of the scan tool. It was quite difficult trying to sort out cause and effect due to not knowing what the system was doing.

Since I already had a laptop, I purchased Scan XL Pro and their OBDLink Scan Tool, both reasonably priced. The latter is the cable that connects the OBD connector in the car to a USB connector on the laptop. It comes with basic software that can read DTCs, display freeze frame data and some component data values. The Scan XL Pro program expands the number of data values that can be recorded, and these recording sessions can be graphed so you can watch for trends and out of range values. Expansion packs are also available for specific makes that provide access to manufacturer-specific data.
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Old 07-30-2017, 06:46 PM   #15
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Default Front motor mount. Dimming lights

Quote:
Originally Posted by 99BonneSLE View Post
What'* going on everyone. Lately, I've noticed my car doing something really weird. Every time I turn the wheel, my oil pressure and battery level drove and my lights dim. I took a video of it. Check it out.

[YT]http://www.youtube.com/watch?v=wL-OZfB14hk[/YT]

Also, sometimes at idle the battery will fluctuate. And when my wipers are on, it fluctuates as well. I don't know what'* going on. But it'* freaking me out. I feel like it'* the alternator starting to go back. I also need a new front bottom motor mount and a lower dogbone as well. . Any help would be greatly appreciated. I need to get it fixed soon. I can't have her dying on me.
I have the same problem with the dimming lights every so often while idling, still trying to figue that one out. The front motor mount is easier to change by putting a jack under the engine and transmission since it bolts to the transmission and then unbolt the drivers side front crossmember after undoing the 3 nuts that bolt the mount to the crossmember. If you try to take it out without lowering the crossmember it will be WAY HARDER to remove and reinstall the new one. It'* so much easier with the front crossmember removed.
MAF sensors are notorious for going bad on these cars. Over time the cheap solder job on Hitachi sensors will disconnect internally from the MAF sensor board. you will have either intermittent problems or no signal at all. NEVER wiggle the connector. Doing so may wiggle the connector pins and break the solder from the board internally. Don't get any from the junkyard, because chances are they will be bad and the reason for the car being there in the first place. I got a new Delphi sensor from Amazon for like $89. Well worth it. My car has throttle response restored. Don't go cheap with the MAF or get off brands. I got a Duralast and it was garbage right out of the box causing surging idle and then the car would die.
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