Code 24???

[TommyL]

I took my 90 out for a spin yesterday after trying to erase the infl rest light grrrrrr. When I come to a stop, the idle goes way down, the "check engine light" and the "ride control light" come on. After driving for a bit to operating temp, the lights go out and all is well...car runs great.

I pulled the codes and have a code 24 "speed sensor". This sensor was replaced about 2 years ago and it might have 5,000 kms on the new one.

Any ideas as to what might be the cause of this code 24 other then the actual sensor itself ? Seems odd that it runs great after it gets to running temp and both lights go out.

As well, If I retrieve the codes and dissconnect the battery...will this erase the codes ? I would like to erase them and see if the code 24 comes back.

Thanks, Tom

[XfireZ51]

I took my 90 out for a spin yesterday after trying to erase the infl rest light grrrrrr. When I come to a stop, the idle goes way down, the "check engine light" and the "ride control light" come on. After driving for a bit to operating temp, the lights go out and all is well...car runs great.

I pulled the codes and have a code 24 "speed sensor". This sensor was replaced about 2 years ago and it might have 5,000 kms on the new one.

Any ideas as to what might be the cause of this code 24 other then the actual sensor itself ? Seems odd that it runs great after it gets to running temp and both lights go out.

As well, If I retrieve the codes and dissconnect the battery...will this erase the codes ? I would like to erase them and see if the code 24 comes back.

Thanks, Tom

Tom,

I would pull battery and see if codes come back. Altho the light goes out the code is still stored. If it comes back after pulling battery then I would go to FSM and follow the diagnostic tree for a Code 24.

[TommyL]

I have done this, could be one of many things and this is very intermitant. The speedo works for a bit after the car is warm, then reads "0" and the lights come on. I am thinking the darn speed sensor is pooched again but wow its not very old and has'nt got many miles on it. :dontknow:

[tomtom72]

Okay as Jeff (Sensi-san) hasn't seen this yet I'm gonna try & run something by you Tom. The VSS is a gear driven mini-alternator yielding A/C voltage, in my mind what's to break? The coil windings? the magnet? IMHO...not too likely...and since the FSM makes no mention of converting the v output to DC there is no rectifier bridge & diode trio to cook...or at least that's how I understand the FSM DTC24 page.:redface:

I'd check the simple things first like the connectors, the VSS plug first, try re-seating the EPROM(?), the 10 pin & 15 pin under the driver's hush panel. Maybe some contact spray cleaner & fresh di-electric grease? Check ECM pins A6 & A11 for dirt or damage(?) and A17 as it's the out to the CCM which eventually goes to the dash speedo display. Okay now I'm a bit lost at this point, sorry Tom. :redface:

This is a bit odd in that the DTC comes after warm-up....I'm stumped on that unless an ECM ground is vibrating loose or a wire is broken someplace...I hate to say this as it sounds silly. Jack up the rear, support the knuckle at level ride height w/more jack stands, start her up, get to temp, 1st gear engaged & let the clutch out and hook up a scanner and see if the scanner is getting a speed signal....but that really isn't for an "intermittent" code....:redface:

I hate electrical issues mostly because I stink at chasing them down, sorry.

[TommyL]

Thanks Tom...thats a great start for me. I will check all this out tomorrow (day off) and post the results. I, like youself, hate anything electrical...I can do almost anything work- wise on this car but electrical no so much.

Thanks again :cheers:

[tomtom72]

:thumbsup:Tom.

I was thinking that if you have the Helm FSM and the use of a scanner, you could hook up the scanner and just drive around with it and save the jacking up part of this mess.

:cheers:
Tom

God, I hate electrical issues!!!!!

[TommyL]

Anyone have the correct 1990 part number for the speed sensor?

[-=Jeff=-]

Anyone have the correct 1990 part number for the speed sensor?

25007308

[Jeffvette]

25007308




Discontinued.

[-=Jeff=-]

Discontinued.

:(

[TommyL]

oh ohhhhhhhhh whatever will I do??? I did manage to get one from GM a few years ago and as i recall it wasnt the same part number as the books called for. hmmmmmm that kinda sucks! another part we will all need at some point.

I will figure something out!

[Jeffvette]

Tom, did your Service ride control light come on and give you a code 23?

[TommyL]

yes and no Jeff, The light did come on but, I didn't get a code 23... I will take it out for run today and check it again. What would a code 23 mean when combined with the code 24? Last time I had it out, the speedo would work intermitently...it would read 0 then would read the proper mph.

[Jeffvette]

yes and no Jeff, The light did come on but, I didn't get a code 23... I will take it out for run today and check it again. What would a code 23 mean when combined with the code 24? Last time I had it out, the speedo would work intermitently...it would read 0 then would read the proper mph.


Code 23 on the SRC is loss of vehicle speed. If you are not setting that code, the issue is not the VSS, as it get the signal from the same source.

[TommyL]

hmmm what would be the most likely cause of a 24?

[XfireZ51]

hmmm what would be the most likely cause of a 24?

That's what the diag tree in the FSM is for.

[TommyL]

Honestly, I havent had time to play around with it yet and I dont have a scan tool. I will have to make time tomorrow to take a serious look into this. I was hoping I could change the sensor and voila fixed....too easy perhaps. :pray

[TommyL]

Ok heres the scoop....When I took the 90 out for a spin today the speedo reads 0 until I get to 30 kms the it reads the actual speed. Once I slow for a stop light to below 30 kms the speedo goes back to 0. When I first set out, the engine light came on about 2 blocks from home, stayed on for about a block then went out and did not come back on. The suspension light did not come on and all 3 settings are working. This is weird as the car, once warm, runs perfect, even the cruise control works. I am currently running a DRM prom and I am going to change it out for the original prom and see if that makes a differance. I have the week off so I can play around with it. GRRRRRR wish I had a scan tool (Tech one) or something to run while driving the car.

[Jeffvette]

Well, if your SRC light is not coming on, you don't have an issue with the VSS.

You really need a scan tool to do the diag correctly. Mainly to see if the speed is being generated. Even if you had a open ckt or grounding issue, the SRC light would illuminate.

Possible issues
Ride controller has gone tits up.
ECM
MEM-cal

Get a hold of Dwight, he has a Tech 1. He leaves for New York on Wednesday. He also is having a code 24 error, but needs to replace his heater core first.

[TommyL]

Fixed!!! Turned out to be the speed sensor after all. When it was taken apart, I noticed the inner gear is chewed slightly and looks like its on its way out. I'm hoping the inner gear will last a few years so when I take it all apart, I can put a new clutch/pressure plate and a short shifter all at the same time.

Thanks for the help Jeff. :cheers: