Transmission problems 4 speed.

[Daren Uzzell]

Hi guys and gals,
I'm still having problems with my 2004 M1097a2 4 speed transmission, the issue was it would randomly drop gear, hunt between gears and not change to top or lock in the torque converter. This happens either if I hit a hard bump (which is pretty easy with the HD springs on the M1097s) or when I accelerate hard.
I have jumper wire diagnosed the issue and it flags up the 71 fault code which is an engine speed sensor (crank shaft) fault. I have followed the trouble shooting guide and checked resistance across the speed sensor plug which was fine, checked continuity from the h pin to the plug and this was fine too. I decided to change out the speed sensor and it has improved things but it is still not 100% and the trans light keeps illuminating. On a test drive it still randomly can not decide which gear to select and will change down then up the down again then will settle on a gear if I slow down.
Any suggestions I'm at a loss now. How can I check if there is a fault with the crank shaft gear which works with the sensor??
Thanks

 

[springer1981]

Hi guys and gals,
I'm still having problems with my 2004 M1097a2 4 speed transmission, the issue was it would randomly drop gear, hunt between gears and not change to top or lock in the torque converter. This happens either if I hit a hard bump (which is pretty easy with the HD springs on the M1097s) or when I accelerate hard.
I have jumper wire diagnosed the issue and it flags up the 71 fault code which is an engine speed sensor (crank shaft) fault. I have followed the trouble shooting guide and checked resistance across the speed sensor plug which was fine, checked continuity from the h pin to the plug and this was fine too. I decided to change out the speed sensor and it has improved things but it is still not 100% and the trans light keeps illuminating. On a test drive it still randomly can not decide which gear to select and will change down then up the down again then will settle on a gear if I slow down.
Any suggestions I'm at a loss now. How can I check if there is a fault with the crank shaft gear which works with the sensor??
Thanks

Based on your description, I would be inclined to look for a wire issue, intermittent short, ground or bad connection in the crank sensor circuit. I wouldn't go after the gear since it would be unlikely to be damaged.

 

[Mogman]

I agree with springer1981, it is extremely unlikely it is a reluctor ring issue, My best guess is also a wiring issue.

 

[Mogman]

Re-seat all the connections after cleaning them with Deoxit and look for wear on the harness.
It could also be a TCM issue not driving/reading the ESS correctly.

 

[Daren Uzzell]

Re-seat all the connections after cleaning them with Deoxit and look for wear on the harness.
It could also be a TCM issue not driving/reading the ESS correctly.

That sound like it could be expensive.

 

[Daren Uzzell]

Thanks, I too am thinking a wiring fault. As it's not all the time and related to bumps. It all started when I fitted new batteries, but I have been through the wiring in the battery box.
I'll clean the plugs and retest the wiring as you have both said.
Thanks.

 

[Mogman]

It uses the same TCM as the civy 4L80 so should not be too expensive, it should have a number on the TCM something like 24230461.
There are 1000 TCMs for sale on Fleabay at this time listed under the example part number.
The tuning might be a little different from TCM to TCM but there are tons of them listed for under $40

 

[TNDRIVER]

Hi guys and gals,
I'm still having problems with my 2004 M1097a2 4 speed transmission, the issue was it would randomly drop gear, hunt between gears and not change to top or lock in the torque converter. This happens either if I hit a hard bump (which is pretty easy with the HD springs on the M1097s) or when I accelerate hard.
I have jumper wire diagnosed the issue and it flags up the 71 fault code which is an engine speed sensor (crank shaft) fault. I have followed the trouble shooting guide and checked resistance across the speed sensor plug which was fine, checked continuity from the h pin to the plug and this was fine too. I decided to change out the speed sensor and it has improved things but it is still not 100% and the trans light keeps illuminating. On a test drive it still randomly can not decide which gear to select and will change down then up the down again then will settle on a gear if I slow down.
Any suggestions I'm at a loss now. How can I check if there is a fault with the crank shaft gear which works with the sensor??
Thanks

Pull the plug where it goes into the case and look for fluid.....dry=good....wet=bad.... my 2 cents