No solution (long)
#1
Registered User
Thread Starter
No solution (long)
I really hate bandaiding problems, but I haven't been able to find and fix my overdrive problem. Here is the problem. If I adjust my TPS any higher than .2 volts, overdrive will not engage unless I let up on the throttle. As soon as I get back on the throttle it shifts out of OD. But the cruise control works normal. If I adjust the TPS down as low as I can without it freaking out because it is off the edge of the resister, shift is normal (kinda) but cruise control runs away.
What I have done so far:
2 different and ohmed good TPS sensors.
Tried the pot TPS delete.
3 different ecms of unknown character.
3 new VSS sensors and I tried the one off my other truck just cuz.
Checked and repaired or bypassed any questionable or bad wires and connectors.
Tried a variable resistor in the 5V line to the TPS.
Only minor changes in how it reacted, not enough to call it even close to fixed. My only remaining option is to control OD external to the ecm.
What I have done so far:
2 different and ohmed good TPS sensors.
Tried the pot TPS delete.
3 different ecms of unknown character.
3 new VSS sensors and I tried the one off my other truck just cuz.
Checked and repaired or bypassed any questionable or bad wires and connectors.
Tried a variable resistor in the 5V line to the TPS.
Only minor changes in how it reacted, not enough to call it even close to fixed. My only remaining option is to control OD external to the ecm.
#2
Have you changed out the od solenoid in the transmission? I had a similar problem and a new solenoid fixed it. You can change it out with out pulling the vb. Just cut the wires and solder the new one in.
#3
Registered User
Thread Starter
The OD solenoid works as advertised when directly connected to a switch. That was one of the many things I tried during trouble shooting. The problem seems to be inside the ecm. I wish I can get a schematic for it. These brainless boxes are 20+ years old now. And I know things like capacitors and coils deteriorate with time.
#4
Registered User
The OD solenoid works as advertised when directly connected to a switch. That was one of the many things I tried during trouble shooting. The problem seems to be inside the ecm. I wish I can get a schematic for it. These brainless boxes are 20+ years old now. And I know things like capacitors and coils deteriorate with time.
Maybe a wiring fault between the ECM and the solenoid. I'm thinking engine rocking on the mounts with torque moving a wire.
#5
Registered User
Thread Starter
Been through each wire, replaced a few, bypassed some connectors. The failure can be tracked to any change in the TPS adjustment which you can't adjust properly. Someone suggested a bad VSS signal to the ecm which both the OD and cruise control use. New VSS and wiring repair VSS to ecm, no effect. Maybe what we are getting for a VSS is not the correct output? I've read voltage output and I've read pulse output. Does the ecm use one and the speedo use the other? Just because all 3 ecms do the same thing doesn't exclude them from being the problem. I have no proof they are good.
#7
Registered User
Thread Starter
When I have the TPS set to 1V at ide, OD will not engage but cruise control works great. When I set the TPS for .2V OD will engage with a slight letup on the throttle, but cruise control will run away.
Trending Topics
#9
Registered User
What's the difference between a first gen and second gen TPS? They look the same.
Adjustment should be 1.0V at idle, and 3.5V +-0.25V at WOT. If it's higher, you'd have the symptoms you describe.
Adjustment should be 1.0V at idle, and 3.5V +-0.25V at WOT. If it's higher, you'd have the symptoms you describe.
#10
Registered User
Join Date: Oct 2010
Location: Oak Hills (Cajon Pass Summit), Ca
Posts: 561
Likes: 0
Received 0 Likes
on
0 Posts
One difference I know is the 2nd gen TPS rotates the other way, the throtte cable pulls the lever from the front.
#13
Registered User
#14
Registered User
#15
Registered User