My 88 IROC 305 TPI 700R4 with 10 bolt 3.73 gears and BM megashifter has stopped locking up the convertor. My mileage has gone to hell and I did the tap the brake test on the highway and had no rpm drop. So where do I begin to diagonse this? Can someone give the basic tests I should run? I just need to know where to start to track down the problem. I have my voltmeter ready.

Thanks
Brian

 

I just checked the fluid level with the car running in park and hot. Fluid level is good.

I then tried a test where I put my voltmeter postive lead in "F" terminal on the diagnostic port and touched the negative lead to ground. I showed a constant 12 to 13 volts on the meter even when I went for a ride on the highway at 65 mph for about 10 minutes. If I understand this correctly I should have had a voltage drop to almost zero when the computer tells the TCC to lock. But I had nothing happen on the highway. What does this mean?

I also checked to make sure the connector plug on the trans was plugged in firmly. It is and the pins did not look bent. At least on the plug side, can not see the tranny side.

Guys help me out here.

 

Call me in the late afternoon PST and I will try to help you out here, 909 7951876. Dana

 

Thanks Dana,

I just tried another test I found in the service manual. With the ign. on test lead to terimnal F and grounded, step on the brake. Light should go out or voltage to zero when I step on the brake. I only have a very slight voltage drop 13.5 to 13 when I step on the brake (indicates brake switch out of adjustment or faulty or circuit 422 shorted to voltage).

Another test I did.
Ign. on, engine off. release brake pedal, ground diagnostic terminal. Light should go out or voltage to zero. Again only slight voltage change. Test again indicates open in circuit 422 or faulty ECM.

What is an open in a circuit mean or shorted to voltage mean?

 

Wow, I am amazed at the lack of assistance from this section on the board. I guess should just ask some useless questions like: Hey, what gear or stall I should run. Will probably get 50 responses on that garbage. I never post in this section and now I remeber why. I will move this TPI or tech section at least someone over there may be able to help. Whoever is moderating this section should feel proud.