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Vehicle speed sensor replacement procedure?


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Danpatters583

Hello again all,

 

My Reatta has a weird issue. When I turn the cruise control on. some times it pulsates in acceleration while trying to keep speed. It flashed the engine light at me once for about 2 minutes then went away. Hasn't come back on since. I checked the codes and it is complaining about the vehicle speed sensor circuit. 

 

My question is how do you replace the speed sensor? Is it a fairly quick job and simple or does it require alot more? It seems to only do it with cruise control on. Other wise it seems to behave just fine. 

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Philbo

What year is your Reatta? I have the factory repair manual for 1990 and can look to see if it has any info on your problem.  

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  • 2 weeks later...
Danpatters583

I appologize for the late reply. My reatta is a 1990. Do you know where its located too?

 

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Ronnie

The speed sensor is shown in the photo below. I doubt it is causing a cruise control problem if the speedometer is working correctly. I would eliminate all other possibilities because it looks like it would be hard to get at to change.

 

Sensor locations.jpg

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Danpatters583
On 2/4/2021 at 12:01 PM, Ronnie said:

The speed sensor is shown in the photo below. I doubt it is causing a cruise control problem if the speedometer is working correctly. I would eliminate all other possibilities because it looks like it would be hard to get at to change.

 

Sensor locations.jpg

I have noticed sometimes in idle the speedometer will show that im moving at 1-2mph. Ive also noticed a slight misfire or hesitation around 50-55mph. Don't know if the two are related. One time it did flash the engine light at me and when I checked the codes it said vehicle speed Circuit. That's why I was curious about the vss. Other than wiring and the body control module I dont know of much else that can cause that code to come on. Am I over looking anything?

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Danpatters583

update but totally different issue. For every one reading this. On my way to work tonight I got an E 041 cam sensor code... So I'm assuming some of the miss fire is coming from it.... 😑 and of course its 20 degrees outside.... Looks like she might be sitting for a while. Until it warms up at least. 

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Philbo
On 2/6/2021 at 1:01 AM, Danpatters583 said:

I have noticed sometimes in idle the speedometer will show that im moving at 1-2mph. Ive also noticed a slight misfire or hesitation around 50-55mph. Don't know if the two are related. One time it did flash the engine light at me and when I checked the codes it said vehicle speed Circuit. That's why I was curious about the vss. Other than wiring and the body control module I dont know of much else that can cause that code to come on. Am I over looking anything?

My spedometer does that occasionally as well, but I do not have the misfire issue at 55 mph you sescribe.

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Danpatters583
1 hour ago, Philbo said:

My spedometer does that occasionally as well, but I do not have the misfire issue at 55 mph you sescribe.

I think its from my cam position sensor. I got a code 41 today. So that's probably where the misfire comes from. 

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Ronnie
7 hours ago, Danpatters583 said:

I think its from my cam position sensor. I got a code 41 today. So that's probably where the misfire comes from. 

You are probably getting the code E041 because the cam magnet in the camshaft gear is disintegrating although you might have a bad sensor which is rare. Instructions are here on ROJ for replacing the magnet without taking the engine apart.

 

Normally the cam position sensor shouldn't cause a misfire. Most people say they have no issues when they have a code E041 other than the annoying warnings you see on the dash.

 

I have disconnected my CPS before just to see what happens. The CPS syncs the timing of injector opening to spray fuel at the optimal time as the intake valve opens. Theoretically that should give a little better performance and fuel economy but I didn't notice the difference in performance when I unplugged mine. I didn't drive it long enough with the CPS unplugged to check fuel mileage.

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Philbo
11 hours ago, Danpatters583 said:

I think its from my cam position sensor. I got a code 41 today. So that's probably where the misfire comes from. 

There is a repair procedure in the how-to that involves gluing a new magnet to the cam sprocket through the hole that the sensor itself sits in.  I just tried it myself and it wasn't too difficult. I haven't started it up yet though.

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Philbo

Yeah I agree with Ronnie. I've been driving mine without the CPS magnet for about a year now and no issues other than less than ideal gas mileage. Although I've never had the cps working so not sure how much better that makes it run.  I get a stumble sometimes from a stop, but she drives nice and smooth at speed unlike the problem you describe. I would eliminate the simple stuff first.  Could be as simple as you need new plugs and/or wires. If that's not it the next thing I would check is your fuel pump/pressure and maybe your coils.  Maybe clean out the throttle body real good as well and make sure the MAF sensor is clean.  Also could be related to a vacuum leak, which could be anything from a loose vacuum line to a bad gasket somewhere. 

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Danpatters583
On 2/9/2021 at 1:59 PM, Philbo said:

Yeah I agree with Ronnie. I've been driving mine without the CPS magnet for about a year now and no issues other than less than ideal gas mileage. Although I've never had the cps working so not sure how much better that makes it run.  I get a stumble sometimes from a stop, but she drives nice and smooth at speed unlike the problem you describe. I would eliminate the simple stuff first.  Could be as simple as you need new plugs and/or wires. If that's not it the next thing I would check is your fuel pump/pressure and maybe your coils.  Maybe clean out the throttle body real good as well and make sure the MAF sensor is clean.  Also could be related to a vacuum leak, which could be anything from a loose vacuum line to a bad gasket somewhere. 

All above have been replaced except some vacuum lines. I suppose that could do it too. I have been reading up on the magnet replacement. Kinda been debating just replacing the magnet or doing the whole job since this car has sat for most of its life. As we all know metal does fatigue over time, even when not in use, timing chains stretch and gears wear out. I haven't done any trouble shooting yet because it is currently -3 degrees outside. And even in my garage that's a bit to cold to do much. When it warms up again ill have to look into it. It does still drive and drives fairly well. Like i said before it really only seems to have the miss fire at about 55. And its only a slight hiccup and continues on just fine. I did just buy a FSM for it so ill have a book to reference stuff too. When it warms up again I will certainly be replacing the cam magnet. 

 

What do you guys think? Do you think its a bit overkill too do the chains? I literally just rolled it over to 65k 

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Ronnie

At 65k I wouldn't replace the chain unless you have reason to believe there is a problem with it. The plastic the magnet elements (4 rods) are housed in disintegrates because of age, not wear, so even if you never drove the car it is possible the cam magnet interrupter could go bad.

 

cammagn2.jpg

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2seater

Typical speed for an ignition misfire to show up is as the car goes to high gear and torque converter locks up, which is around 50 mph at minimum throttle. Light cruise and perhaps a slight incline will show an imperfect ignition.

 

 I doubt the timing chain and sprockets need replacement. The only time that would make sense is if opening it up to replace the magnet. Most metallic parts are pretty impervious to storage as long as protected from corrosion. 

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Philbo

Mine is at about 137k and I decided to do the JB weld repair instead of replacing the whole chain and sprocket. Kind of a subscriber to the "ain't broke don't fix it" mentality. I mean I was surprised how straightforward the jb weld repair was. I mean even if you only got 20k miles before you then had to do the chain, that's 2+ years of driving out of a relatively simple repair (much simpler that the whole kit and kaboodle that's for sure).  Also, I've owned a number of older GM cars, all higher mileage (highest is 250k) and I have yet to have to do a timing chain on any of them.

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Danpatters583
4 hours ago, Philbo said:

Mine is at about 137k and I decided to do the JB weld repair instead of replacing the whole chain and sprocket. Kind of a subscriber to the "ain't broke don't fix it" mentality. I mean I was surprised how straightforward the jb weld repair was. I mean even if you only got 20k miles before you then had to do the chain, that's 2+ years of driving out of a relatively simple repair (much simpler that the whole kit and kaboodle that's for sure).  Also, I've owned a number of older GM cars, all higher mileage (highest is 250k) and I have yet to have to do a timing chain on any of them.

I guess I'm just being too paranoid that if i don't replace the chain that something will go wrong and warrant me to replace it anyway. My luck usually seems to run that way 😅. I have all gm vehicles except my neon and 928 as well. And ill admit ive only had to do a chain set once on my nova. Then again I was rebuilding it so made no sense to reuse an old set. I guess im just being overly paranoid. I will do just the magnet repair. See how it goes. 

 

As for the ignition system as mentioned earlier now that i think about it, that very well could be the issue. I bought cheap coils off eBay... Came as a kit with the icm for 85 bucks. Ill have to look into that later. First thing is first. Ill do the cam magnet. Then look at everything else. Ill post with updates when it warms up.

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Philbo
9 hours ago, Danpatters583 said:

I guess I'm just being too paranoid that if i don't replace the chain that something will go wrong and warrant me to replace it anyway. My luck usually seems to run that way 😅. I have all gm vehicles except my neon and 928 as well. And ill admit ive only had to do a chain set once on my nova. Then again I was rebuilding it so made no sense to reuse an old set. I guess im just being overly paranoid. I will do just the magnet repair. See how it goes. 

 

As for the ignition system as mentioned earlier now that i think about it, that very well could be the issue. I bought cheap coils off eBay... Came as a kit with the icm for 85 bucks. Ill have to look into that later. First thing is first. Ill do the cam magnet. Then look at everything else. Ill post with updates when it warms up.

Just a couple tips on the cam sensor magnet. I found it helpful to get the coolant overflow tank out of the way as well as the water pump pulley to give a little more room to work. I didn't disconnect the tank, just took off the black bar that goes across over the battery and then the two fasteners that hold the tank in. Then you can kind of just move it out of the way.  I cleaned the remaining plastic pieces of the magnet carrier out with a combination of a short screwdriver and some needle nose pliers. I tried to extract what I could, but you are bound to drop some down into the oil pan. I'm not worried about it. The strainer on the oil pickup will catch them.  I used acetone and cotton swabs to get the surface nice and clean for good adhesion with the jb weld and I used a file to file down the flange on the magnet. Also I used a magnetic pickup tool similar to the one in the instruction to put the magnet in. That worked great.

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Danpatters583
On 2/13/2021 at 9:13 AM, Philbo said:

Just a couple tips on the cam sensor magnet. I found it helpful to get the coolant overflow tank out of the way as well as the water pump pulley to give a little more room to work. I didn't disconnect the tank, just took off the black bar that goes across over the battery and then the two fasteners that hold the tank in. Then you can kind of just move it out of the way.  I cleaned the remaining plastic pieces of the magnet carrier out with a combination of a short screwdriver and some needle nose pliers. I tried to extract what I could, but you are bound to drop some down into the oil pan. I'm not worried about it. The strainer on the oil pickup will catch them.  I used acetone and cotton swabs to get the surface nice and clean for good adhesion with the jb weld and I used a file to file down the flange on the magnet. Also I used a magnetic pickup tool similar to the one in the instruction to put the magnet in. That worked great.

Sweet. Thanks! I'll let you guys know next week how it turns out. Its supposed to get up to the 50's here next week. Perfect temp for working lol

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Danpatters583

Great news every one. It finally warmed up enough and I mustered enough energy to go out and replace the cam Sensor interrupter. Turns out its much easier than it looks from the write up. seems to be holding up well so far. Code went away immediately. Also swapped the coils out for some oe ones to see if my slight miss at about 55 mph goes away. Thank you all for your help once again. You guys are great! Also for future reference I now have a FSM for the car so if any one needs any repair info for a 1990 model I would be willing to share the info if any one needs any. 

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Ronnie
2 hours ago, Danpatters583 said:

Turns out its much easier than it looks from the write up.

Any tips you can give on improving the instructions for replacing the magnet to make them better?

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