97 Aurora Speedo/Cruise Control VSS Issues - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 07-22-2014, 09:45 PM   #1
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Default 97 Aurora Speedo/Cruise Control VSS Issues

Hey everyone,

So my Aurora has been running just fine up until my radiator started leaking. Patched it just fine 2 days ago and haven't had any issues since, has never run better.

Yesterday I hosed down the engine compartment since the engine was covered in antifreeze - no problems after that at all, some condensation got into the headlight housing and a bulb blew but it could have been a coincidence. It dried quickly in the sun and I did not drive it until it was completely dry so I doubt that has much to do with the problem.

Today, I installed the new bulbs and sprayed a bit (okay, maybe a lot) of Fluid Film on the bolts and other moving parts. When I started the car and started driving, I noticed the speedometer jumping around, sometimes just going to zero as though there is an intermittent connection. It then stayed at 0 and I drove it back home to take a closer look.

Pulled out my code reader and sure enough, there was P1642 I think, something to do with the VSS sensor signal.

Though Fluid Film is supposed to be non-conductive, I thought it may be affecting a ground. So, I went back and sprayed all the ground bolts and wires and pretty much anything electrically related with MAF cleaner and that got rid of any residue.

It seemed to have helped, though the speedometer still moves slowly when going back down to zero. I'm still getting occasional dropouts and sometimes it starts jumping again.

The cruise control does not work - when I press the button, the "cruise" light comes on for as long as I hold down the button but it does not actually activate. At 40km/hr or below it does not come on at all, which is normal, of course.

The onboard computer reports intermittent very low fuel consumption even though I am driving uphill. The odometer seems to work just fine.

On the highway, the car once jumped into 3rd gear even though it'* never done that before.

I can't get the VSS sensor code to come back up even after the mis-shift.

So I'm pretty sure somewhere a wire to the VSS sensor must be damaged - where should I look? Should I just leave it in hopes it'll cure itself after a couple hours of sitting? Spray some more cleaner? Hose down the engine again?

Thanks so much!
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Old 07-23-2014, 12:04 AM   #2
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Update: A short while later and a little more cleaning what I thought might be the VSS sensor on the passenger side visible when turning the wheel all the way to the left, I'm no longer getting any jumping or dropouts. Something still doesn't feel right and the needle does seem to be slow especially noticeable when I've come to a stop, as soon as the car is stationary it'll still be at about 5 km/hr then drop to 0, and it does not sit on the peg, rather near the top of the zero mark. MPG is more accurate but still a little iffy I think.

I can't remember how it was before the problems started so it could be normal. The cruise control still does not work but I could have broken the module when I washed the engine since I don't remember trying it out then.

Another weird thing, I got for the first time, before cleaning it again the message "engine hot...a/c off" and a random RPM jump and the fans came on even though the engine was only 1 tick mark above the centre point which this car usually runs at in stop and go and I'm pretty sure the A/C wasn't even on! I do remember getting a similar message when I first got the car about 9,000km ago but it quickly disappeared and haven't seen it since.

If the problems don't clear up by themselves I might have to bring the car to a mechanic as electrical problems are an absolute nightmare to deal with.
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Old 07-23-2014, 07:24 AM   #3
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some of these cars have two temp sensors, one for the gauge and one for the computer. if there is an issue with the one for the pcm or the wires for it come loose it will give you that message and turn on the fans, its sort of a safety mode. so i would clean the connector for that sensor and inspect the ect plug and wires to pcm
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Old 07-23-2014, 04:25 PM   #4
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I think I'll leave that issue for now and look into it if it comes up again, I did end up pulling a code P1536 related to the engine temperature.

So this morning the cruise control started working again (not anymore, read below), to my surprise, but the speedometer was still slow. I think it'* got to be the wiring I just don't know where to look because there'* hardly any diagram showing where the wire travels. It could be the sensor itself I'm just not sure how washing the engine or oiling parts could damage the actual sensor when it is well out of view, the wiring seems much more likely to me.

The speedometer seems to show the correct speed but it'* slow to react especially noticeable with sudden changes. It'* like there'* a damper on the needle.

After the car sat for 6 hours, the cruise control no longer works! There are no codes I can pull and after pushing the cruise button a couple of times the light no longer flickers, it just stays off.
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Old 07-23-2014, 05:12 PM   #5
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i would try to find someone with a live data capable scanner, so you can compare pcm vss reading with the cluster reading.
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