Mishako129

I have a 91 accord lx wagon. I got this problem now with my automatic transmission. It seems like its slipping when going from 1st to 2nd, its like its in neutral and it can't find the right gears. The speedometer is not working either. I pulled the codes and it listed a code 4, which is a speed sensor, and a code 15.

Both of these problems started happening after I drove on the highway. Specifically it was after I downshifted to pass a semi that was in the right lane. It was at 4,000 rpms at about 55 mph. Now my transmission is acting bad.

It doesn't slip all the time it just seems to whenever the speedometer stops working.

Last Fall I had the same problem except it was only with the speed sensor. I found out one of the pins on the wiring connector going to it was completely missing. To fix it I put some old wiring in the place of the pin and it worked. Now the problem has come back to haunt me.

In my official Helms manual, a code 15 for S light is,

-Disconnected NM speed sensor connector
-Short or open in NM speed sensor wire
-Faulty NM speed sensor

Symptom - Transmission jerks hard when shifting


Code 4 S light is the exact same thing except it has a different symptom,

-Disconnected NM speed sensor connector
-Short or open in NM speed sensor wire
-Faulty NM speed sensor

-Symptom - Lock-ip clutch does not engage





I did check the ohms resistance of the speed sensor as the Honda manual told me to and it registered 1091 ohms. The manual said it should have been a 400-600 ohms reading. Does this mean my speed sensor is fried? If it is not bad, the manual instructs me to check the TCU terminals for continuity as well.


I think it was the faulty speed sensor connector with the missing tooth that caused the problem. I did measure the connector and found it had a 17 ohms reading, so there was continuity. I found one on ebay. I should be able to graft this into the wiring harness easily right?

http://www.ebay.com/itm/VSS-SPEED-SENSOR-WIRING-PLUG-HONDA-CIVIC-INTEGRA-VTEC-3-WIRE-OEM-ACURA-/221195213463?pt=LH_DefaultDomain_100&hash=item3380431a97&vxp=mtr

This a 3 WIRE VSS VEHICLE SPEED SENSOR WIRING PLUG FROM A OBD1 1995 ACURA INTEGRA B18b1 LS

MAD_MIKE

May just need to fix it with a proper pin, the wiring may have come loose or corroded.
The NM sensor could also be fouled with ferrous material, it is a magnet. Pull it out of the cover and clean it off, same with the NC sensor, if one is fouled up the other is probably in similar condition. You will need to replace the O rings, otherwise the sensors will leak.

As for resistance, that 400-600Ω is at 20°C. If the component temperature is different from 20°C then the resistance will be different. Sorry don't know off the top of my head which way the resistance goes compared to temperature change.

With two of the three shaft speed sensors not working, the computer does not know what the transmission is physcially doing.
The TCU is working blind. That would explain the weird shifting.

Mishako129

So can I just replace the pin or do I have to replace the whole plug? I ordered that plug from ebay already. Can you tell me if it will work for my harness?



So the NM sensor is the one that is external and the NC is the one internal? I would doubt the sensors themselves are bad because it is a low mileage JDM transmission and the sensors are not very used at all. Its possible but not likely that the speed sensors are faulty... Unless they shorted out from the missing pin.
So there would be a very different reading depending on the temperature outside?. The temperature outside was only about 60 degrees when I tested the extrenal speed sensor.

Thank heavens that its not a mechanic problem. So you say there are 3 sensors, where is the 3rd?

Like I said though, there is missing pin in the connector. Would the missing pin cause a sensor to go bad or short out? And can I replace the pin or would I need to get the whole plug?

Mishako129

I'm finding it impossible to get to the NM and NC sensors, do I have to approach them from underneath with the car on stands?

Another thing just as important and even more so, do you think its safe to drive the car when it does the weird shifting? I drove it today and it 'slipped' and was malfunctioning trying to find gears. It didn't feel good at all. Is that bad?


I can't find NM speed sensors anywhere I look, I do have an extra one on my old transmission though. So you mean its likely fouled with "ferrous material"? What does that look like, is it black or silvery color? I just pulled the NM sensor on the old transmission and it had a silvery, oily material on it. They were working fine far as I know last time I used it.


Thanks a lot mad mike, looking forward to your next reply. You seem to be the right one to ask for this.

Mishako129

O and another thing, when the speedometer stops working completely (at 0 zero) the car will shift perfectly fine. Its when the speedometer is jumping very very erratically that it will not shift properly and jerk, slip, and / or miss gears. This happens for 5-10 seconds then it usually goes away. I need to know if this is harmful so I can know to unplug the speed sensor.

Mishako129

I just cleaned the NM and NC sensors and took it for a test drive... Nothing, it did not fix it. I also took a continuity test of the two sensors, the both check okay as the instruction said. They were between 400-600 ohms. The sensors themselves did not have hardly anything on them and the gaskets were still good too (low mileage unit).

They VSS (the main one) is the one that I am suspicious of. When I took a continuity reading it was 1091 ohms. Way too high.

Do you think its that which is causing all my woes? Either way i'm going to replace it. I got the one from a 90-93, this is a 96' model, the guys at another forum said it would work, I wanna be sure though. I got the 90-93 model because it has a cord for the connector, thought I would need that for when I spliced the new harness adapter, more wires. And about that, turns out that one of the pins for the VSS wiring harness was not missing at all, it had only fallen out of its bore! So it wasn't the missing pin AT ALL that was causing my problems.

So what do you think, is it the VSS that is broken? I think it fried out because I spilled a bunch of power steering fluid on it 5 months back. When I took it off I could smell it and there was nasty gunk in the sensor itself and where its seated. I cleaned it out but it still did not work.

MAD_MIKE

If it's only the speedo acting up(and not the tach or any other gauges) then I would suspect the VSS is bad, the code 4 pretty much verifies that.

IIRC the 90-93 models you can remove the pickup from the assembly with three screws. You could try taking it apart and seeing if there is anything in there that can be cleaned, but as you stated it is way outside of resistance spec so it more than likely just needs to be replaced.

If you need to drive the car, I would leave the VSS unhooked, when it does work it's erratic output is giving the TCU a false signal. This will cause the erratic shifting which will cause undue wear and tear on the transmission.
I am unsure of what, if any, limp mode the TCU may go into without the VSS.

Mishako129

Thnks madmike. The "undue wear and tear" on the transmission kind of irks me a little, what's the worst it could have done to itself? I mean, I wonder if anyone has sustained real damage from such a thing. One would think the TCU has programs that keep it from damaging itself, and that its made to prevent that from happening.

The oil cooler I installed on there yesterday should help though. I would like to know what exactly the transmission was going through when it was slipping, missing and malfuntioning. Can you show me a diagram of what happened and what the possible "wear and tear" might be?

MAD_MIKE

With the VSS giving erratic signals, the TCU may calculate the car is at a different speed from actual. This would cause a shift into an incorrect gear. Being in the incorrect gear for a given speed would just cause excessive engine speeds. Shifting is where the wear and tear of an AT is. The ON/OFF of clutch pack engagement is where the wear is. But if the TCU was under the impression that the car should be in first because it 'thinks' the car is at a lower speed than actual would be dangerous. Imagine cruising at 55MPH and the TCU recieves a signal that you are doing 5MPH. It may command a downshift to 1st while at speed. Now I do not know if this is a possible failure mode with the 90-97 Accords. But IIRC Toyota had an issue like this a few years ago where a faulty sensor could lead the car to think it was in a lower speed than actual. Such a dramatic change in wheel speed would cause for loss of control.

If the car runs fine, less speedometer, with the VSS disconnected, I would leave it off til you can replace the sensor.

MAD_MIKE

http://techauto.awardspace.com/vss.html

Thought I posted that link.