AAMCO Check Engine Light Transcan results

[jsxr14s]

Greetings everyone!
Had my car checked at AAMCO for their Free Promotional Transcan Inspection.
The code received for the results was the "Speed Sensor Circuit Error."
The AAMCO rep told me that they still don't know what the exact problem is. And that sometimes the code may be able to to tell you exactly what the problem is depending on the code. However of course, in my case, I was blessed to have a more complex code/issue and apparently need to have further inspection/ diagnostic check to find exactly the issue.

I don't mind doing everything necessary to fix my baby. But because of the newb that i am, i am hesitant to go ahead and jump on his offer to test and inspect further for $200, something I don't really know what I'm paying for.

What does this mean exactly? "Speed Sensor Circuit Error"
Major/minor problem? Who, where else can i take it, can I fix it myself with help of course? Or should i just have AAMCO take care of it?

[devnull]

If I remember it correctly, the speed sensor signal goes from the speed sensor to the speedometer and then to the computer.

It could be a wiring fault between the gauge cluster and the computer.

Should be relatively simple to fix.

[DreamN]

What was the actual code? Whatever code given to you seems to not even match up with any of the Nissan's 240SX OBD 2 Codes.

I searched and the info you've given is linked to code P1502, but that isn't for a Nissan as far as I know.

[GSXRJJordan]

S13 or S14?

On a S14, the VSS goes to the lower harness, then the body harness, then the SMJ, then the ECU and the cluster. I don't believe the VSS will throw a code though, so maybe there's something else going on?

Russ can definitely help out here.

[DreamN]

His profile states he owns a s14 zenki so it can be either OBD1 OR OBD2. VSS codes are 14 (OBD1) and P0500 (OBD2). Russ could definitely help with this as I can't find anything to help this guy with what he's given us.

What's the actual issue with the car? Just has the CEL/MIL on?

[projectRDM]

VSS signal goes to the cluster first, then to the ECU. It's a single wire from the cluster (yellow/green), while two wire to the cluster (red and red/yellow).

The CEL will trip if there is no signal to the ECU.

[jsxr14s]

The information I'm giving you guys is all the info I got.
Who is Russ?
New battery and new alternator. But light came on before alt went bad.
Umm but other then that, zenki s14 runs fine. Granted I've only had it since december.
Just a small oil leak.
But what does this exactly mean? And electrical problem? Is it serious?

[devnull]

Yes it's an electrical problem. It won't affect how your engine runs, but you will not be able to pass SMOG with that error code and the check engine light on. Also, the ECU will not limit your speed without a speed sensor signal.

[WoolyS14DET]

They will check the light for free but then will want to charge you a diag fee.
Nothing is free.

Have you even done a visual inspection of the harness ?? it could be pinched ??
get it to someone who knows what they are doing. im sure some of the guys here on zilvia are willing to help you out for half that price if not for some beer ???
You a little far from me other wise I would help you

[DreamN]

VSS signal goes to the cluster first, then to the ECU. It's a single wire from the cluster (yellow/green), while two wire to the cluster (red and red/yellow).

The CEL will trip if there is no signal to the ECU.

Russ, if it was indeed a VSS code wouldn't his speedometer not read correctly or at all? I've read that sometimes it'll just cut out from time to time (ex. driving at 60 mph, hit a bump and then drop to 0 mph and back to 60 mph).

[projectRDM]

Russ, if it was indeed a VSS code wouldn't his speedometer not read correctly or at all? I've read that sometimes it'll just cut out from time to time (ex. driving at 60 mph, hit a bump and then drop to 0 mph and back to 60 mph).

Not always. If the wiring fault is after the cluster the speedometer will read fine but the ECU won't get a signal. If it's before the cluster, yes. The CEL will trip if the ECU doesn't see the signal, so if it's on it could be on either side of the circuit.

Battery and alternator have nothing to do with the VSS circuit. Only the VSS, the speedometer, and the ECU share the same path.

[jsxr14s]

Russ, if it was indeed a VSS code wouldn't his speedometer not read correctly or at all? I've read that sometimes it'll just cut out from time to time (ex. driving at 60 mph, hit a bump and then drop to 0 mph and back to 60 mph).

my speedometer does NOT read correctly sometimes. It does trip out. (i.e. I'll be driving and it'll stay at 0 mph, then all of a sudden i'm on the freeway and jump to about 60 mph)

[jsxr14s]

They will check the light for free but then will want to charge you a diag fee.
Nothing is free.

Have you even done a visual inspection of the harness ?? it could be pinched ??
get it to someone who knows what they are doing. im sure some of the guys here on zilvia are willing to help you out for half that price if not for some beer ???
You a little far from me other wise I would help you

anybody want to get a beer?

[projectRDM]

The VSS is on the way out. Since the signal is erratic, the speedometer fluctuates as well as the ECU input, triggering the CEL. Replace it. It's very unlikely any of the wiring is damaged.

[DreamN]

my speedometer does NOT read correctly sometimes. It does trip out. (i.e. I'll be driving and it'll stay at 0 mph, then all of a sudden i'm on the freeway and jump to about 60 mph)

Dude, you just wasted so much time. Should have mentioned this in the first post and you would have had 20 responses with check your VSS (Vehicle Speed Sensor).