Exhaust Gas Temperature Sensor?

[Zesty]

Car is a '92 base model fastback with 211,000 miles. When I bought it, the CEL was on and giving me a 32. EGR Malfunction.

I took it to a shop, and watched them test it. They basically did what the FSM suggested. Pushed up on the egr diaphram, checked the vacuum hoses and everything checked out fine. HOWEVER he DID NOT test the Exhaust gas temp sensor, so I am figuring this or maybe a faulty ECU.

My car needed to be smogged since I just bought it, and the CEL was still on. The mechanic asked me if I wanted him to clear the light and try to smog it. He did and it passed. So I'm happy about that. From what I understand, my car probably wouldn't pass smog if the EGR was in fact malfunctioning, so I'm figuring it is the temp sensor. Under my car about halfway back, there is a sensor hanging below the exhaust pipe....is this the exhaust gas temp sensor? If one is bad, how much do they usually run to replace?

I am also getting a code "14", vehicle speed sensor open(?), and the mechanic said the only times he has sen this code, is on a car whose speedo did NOT work....mine works, but I'm getting the code anyways. How bad is it to drive the car with a code 14? Thanks.

[g6civcx]

Same response as this guy on the VSS. http://www.zilvia.net/f/showthread.php?t=105479

If you have a CA car, then yes go ahead and check the EGT sensor.

[Zesty]

^Do you know if it could cause any damage or longterm harm to drive the car with the VSS not working? And also, seeing as how my speedo still works, doesn't that mean the VSS is not messed up?

How important is the EGT sensor? I see it is for CA cars only, like the EGR, so I figure it must not be that crucial except for emmissions....which I just passed so if that's the case no big deal for the time being. I don't mind the CEL being on, I just don't want to be doing damage to my car by driving it with these things potentially being faulty.

[g6civcx]

Driving with the VSS unplugged from the ECU won't do any damage. People bypass the speed limiter by doing that. As long as your speedo/odo works you're okay.

I would get that EGT checked. It doesn't really do much, but it may throw a code which will cause you to fail due to the CEL.

Try to figure out why the VSS signal and EGT signal are screwed up. If you only have to do a visual then you can unplug the CEL light bulb temporarily :)

[Zesty]

^Thanks for the help. Sorry if I was unclear, but my car has actually already passed smog just the other day, so I'm not worried about that. That's kinda why I'm confused!

I am getting a code 32 and 14, yet I passed smog and my speedo works.

So I'm guessing I shouldn't be too worried driving my car?

[Zesty]

So is it pretty clear-cut, if my speedo is working than my VSS is fine? or could my speedo still work and the VSS actually be messed up?

[Torrid]

I know this is an old thread, but I'm having the same issue on a '96 S14. I'm getting a VSS code, speedometer reads fine, correct and never has acted up. I was originally told that a controller module for the gauge cluster was the culprit. Replaced it and it worked well for a while and passed emissions that way, but the code is back again and still the speedometer is showing no sign of problems. This weekend I'm going to get the car in the air, check the plug and pull the speed sensor to check it out, but I would think the speedometer would be acting screwy.

[g6civcx]

I know this is an old thread, but I'm having the same issue on a '96 S14. I'm getting a VSS code, speedometer reads fine, correct and never has acted up. I was originally told that a controller module for the gauge cluster was the culprit. Replaced it and it worked well for a while and passed emissions that way, but the code is back again and still the speedometer is showing no sign of problems. This weekend I'm going to get the car in the air, check the plug and pull the speed sensor to check it out, but I would think the speedometer would be acting screwy.


The circuit goes like this:

VSS -> speedometer -> ECU

The speedometer working and the ECU throwing a code leads me to suspect that there is a problem with the VSS signal from the speedometer going to the ECU. Check your dash harness.

I'm not sure what the ECU does with the VSS signal, but that's what I would suspect.

[juls213]

Hi I am a professional tech and I had that same code for vss on a I30 98, this what is happening you have an intermittent open for the vss circuit. The actual sensor is fine because you have a reading on the speedometer. What is happening is there is 4 sodering points in back of the speedometer, these go bad causing the ecm to trow a CEL because it does not see a speed signal. You can either get a new speedometer or solder these 4 points. GOOD LUCK

[g6civcx]

Hi I am a professional tech and I had that same code for vss on a I30 98, this what is happening you have an intermittent open for the vss circuit. The actual sensor is fine because you have a reading on the speedometer. What is happening is there is 4 sodering points in back of the speedometer, these go bad causing the ecm to trow a CEL because it does not see a speed signal. You can either get a new speedometer or solder these 4 points. GOOD LUCK

Excellent tip. Check the connection between the speedometer and the ECU for shorts.


BTW, do you know what the ECU does with the VSS signal?

[Torrid]

The circuit goes like this:

VSS -> speedometer -> ECU

The speedometer working and the ECU throwing a code leads me to suspect that there is a problem with the VSS signal from the speedometer going to the ECU. Check your dash harness.

I'm not sure what the ECU does with the VSS signal, but that's what I would suspect.


That's exactly what I didn't want to hear. The gauge cluster was replaced because of this issue two years ago. I think I'll find that plug underhood first and only pull the gauges if I can't find the issue inline to the ECU.

[g6civcx]

That's exactly what I didn't want to hear. The gauge cluster was replaced because of this issue two years ago. I think I'll find that plug underhood first and only pull the gauges if I can't find the issue inline to the ECU.

If you want to check the VSS, pull the harness that sits near the fuel filter area and check the resistance going across the 2 pins.

Standard Nissan VSS should register 200-300 Ohms.

I highly doubt that's your problem because the speedo is working. I think it's between the speedo and the ECU, but I could be wrong.

[Torrid]

Ok, I believe I've found the VSS from the trans into the back of the gauge cluster, I got 308 ohms if I've found the right wire, it's red/yellow in a ten pin white plug. My question is if this information is correct is what wire is the one going from the gauge cluster to the ECU? This keeps failing so I'd prefer to make a jumper from the trans VSS wire to the ECU VSS wire.

[Torrid]

Ok, from what I've read, it sounds like the wire from the cluster to the ECU is yellow/green and in the same harness. It looks like the unit converts resistance into AC voltage to be read by the ECU. I haven't tried to test it while rolling, but at rest it is reading 10.9 volts DC. Is this high/low, what should I be seeing here? Is it something I won't be able to see what's wrong without driving the car to read? I basically have about another week to figure out this issue, fix it, and have it ready for emissions.

[g6civcx]

This keeps failing so I'd prefer to make a jumper from the trans VSS wire to the ECU VSS wire.

The VSS generates pulses. The speedometer displays the pulses and converts into a digital signal for the ECU.

Fix your speedo to ECU connection.

[stinky_180]

sorry to thread jack and be off-topic but......

is it possible to connect an EGT guage to the EGT sensor wiring harness on the egr valve?

[orion::S14]

^^^ No.

The EGT sensor is on the intake manifold, between runners 2 and 3.

It every once and awhile chekcs to see if the intake air temps are higher than normal when the EGT valve *should* be open...to help diagnose function of the EGR system.

Your next question: Could you use it for IAT...???

Answer: Probably not...b/c you'll never find a gauge that reads the same output.

- Brian

[g6civcx]

sorry to thread jack and be off-topic but......

is it possible to connect an EGT guage to the EGT sensor wiring harness on the egr valve?

Yes, just connect the wires.

Will the gauge read the correct EGT? No.

[Torrid]

Does anyone know what reading I should be getting on the VSS between the ECU and speedometer at rest and moving at a certain speed? I'm trying to figure out what is going on with this thing before I spend $190 on a new speedometer head that was replaced two years ago.

Emissions can't fail me for a VSS code can they? It's not emissions equipment so I would think no. The light on drives me nuts, but knowing I just replaced this part two years ago, I hate to do it again when the gauges are working perfectly fine. I'll still fix it, but I don't want to rush around this week to get the part and replace it in time if it's not necessary.

[g6civcx]

Does anyone know what reading I should be getting on the VSS between the ECU and speedometer at rest and moving at a certain speed? I'm trying to figure out what is going on with this thing before I spend $190 on a new speedometer head that was replaced two years ago.

Emissions can't fail me for a VSS code can they? It's not emissions equipment so I would think no. The light on drives me nuts, but knowing I just replaced this part two years ago, I hate to do it again when the gauges are working perfectly fine. I'll still fix it, but I don't want to rush around this week to get the part and replace it in time if it's not necessary.

Nobody knows. You need a digital data logger to look at the square wave going from speedo to the ECU. So far no one cares enough about it to take readings.

Just pull out your speedometer and check the back of it where it connects to the cluster harness. Then trace the wire to the ECU.

It's just one wire.

[Torrid]

I went through the car and the signal is making it to the ECU, made sure everything was tight. I reset the codes, now I'm getting the IAC code again, VSS code hasn't come back, and I'm getting like 5 other random codes that make no sense to me that I won't even bother to list because they all seem like random crap, including some Dual alternator upper fault. I'm starting to think something is wrong with the ECU and I'm really losing patience with this thing.

[g6civcx]

Make sure that the ECU plug is tight. Otherwise, the ECU may have problems.

[Torrid]

After this happened, I pulled the ECU plug, made sure all the pins were straight, plugged it back in and tightened down the bolt that holds the plug in. I'm hoping that's the end of that.