VSS, 1227727 ECM, and crazy speed readings
06-01-2003, 04:17 PM
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VSS, 1227727 ECM, and crazy speed readings
This is a tricky one.
My truck is using a vehicle speed sensor (VSS) from a 93 Typhoon.
With my old ECM (1227165) I ran a signal from the VSS to the VSS buffer, then from the buffer out to the cluster and ECM. This ECM did not support a signal directly from the VSS, so the VSS buffer had to be used.
My new ECM (1227727) accepts a signal directly from the VSS. Today I ran the wires from the VSS into the ECM. I'm now getting ridiclous speed readings. For example, the shift from park to drive will move the wheels just enough to register about 11mph! If I go for a drive the ECM will max out reading speed at 255mph in no time!
I'm guessing the problem lies at the VSS. The ECM must be receiving an incorrect signal. If you agree that this is the problem, what needs to be changed in the tailshaft (of the transfer case)?
Other comments:
The speed readings I'm looking at are through my laptop, directly from the ECM. The instrument cluster reading is roughly the same. The problem is unrelated to the instrument cluster.
I've swapped through the following ECMs... 1227165 -> 1227730 -> 1227727. With the 1227730 ECM (using the VSS buffer) I was able to get accurate speed readings. With the 1227727 ECM, I could find no way to give it a signal from the VSS buffer. That is why I have tried to eliminate the VSS buffer. I've been told that the 1227730 ECM is the same (internally) as the 1227727 ECM. I'm not so sure about this anymore.
I need to fix this problem so I can move on to getting the torque convertor lockup working properly.
My truck is using a vehicle speed sensor (VSS) from a 93 Typhoon.
With my old ECM (1227165) I ran a signal from the VSS to the VSS buffer, then from the buffer out to the cluster and ECM. This ECM did not support a signal directly from the VSS, so the VSS buffer had to be used.
My new ECM (1227727) accepts a signal directly from the VSS. Today I ran the wires from the VSS into the ECM. I'm now getting ridiclous speed readings. For example, the shift from park to drive will move the wheels just enough to register about 11mph! If I go for a drive the ECM will max out reading speed at 255mph in no time!
I'm guessing the problem lies at the VSS. The ECM must be receiving an incorrect signal. If you agree that this is the problem, what needs to be changed in the tailshaft (of the transfer case)?
Other comments:
The speed readings I'm looking at are through my laptop, directly from the ECM. The instrument cluster reading is roughly the same. The problem is unrelated to the instrument cluster.
I've swapped through the following ECMs... 1227165 -> 1227730 -> 1227727. With the 1227730 ECM (using the VSS buffer) I was able to get accurate speed readings. With the 1227727 ECM, I could find no way to give it a signal from the VSS buffer. That is why I have tried to eliminate the VSS buffer. I've been told that the 1227730 ECM is the same (internally) as the 1227727 ECM. I'm not so sure about this anymore.
I need to fix this problem so I can move on to getting the torque convertor lockup working properly.
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