Pontiac Repair: ignition modual fatlure, speedo sensor, voltage spike

Question
QUESTION: My wife has a 94  pontiac grand am this morning the icm fried I replaced it ...the engine started for about 15 seconds then died now the new icm is fried too(I know this because after it died then the fuel pump would not run again)the fuel fump is new the relay is new the coils are new the computer was replaced 10 months ago and have had problems with the speedometer jumping around when at speeds around 55-60mph I disconected the battery for 30 min and this fixed that temporarily. could this be my problem I am about to lose it with this POS also the transmission was locking up in two gears and the torque converter was locking all at once before resetting the computer by disonnecting it(this was causing the ignition fuse to blow) I cant think of anything else that might be pertanante

ANSWER: Hey mark:

Sound like it's a basket case. Is this a 4 cylinder or a V6? have not seen repeat ICM failures in these. lots of ground wire issues on the engine to tranmission studs by the starter for both 4 and 6 cylinders. if the speedo is acting up it couls be something as simple as the speedo sensor or the reman ecm you put in this is acting up that can cause all kinds of TCC issues if the speedo is erratic. Especially if the ECM was a reman from CARDONE! The ECM is the buffer for the speed senosr tso that is a likely cause but again look at the ground wires give them a tug if they break off start there. if the look green and schhesy looking replace them. good luck :-)


---------- FOLLOW-UP ----------

QUESTION: 1. how hard is the speed senser to replace and this is aq 2.3 SOHC problem child(POS)    2. Is the ECM is able to send a high enough voltage spike to fry the icm.  3 Might the ICM still be ok or am I stuck for another 150 bucks

Answer
The speed sensor is just held intop the transmission by 1 bolt pretty easy to change but I doubt that is your issue. The ecm I doubt fried your ICM I guess in reality it could happen. More of an issue with cheap aftermarket parts would be my guess. Are you sure that is your issue here you have no spark? what about injector pulse? The ICM buffers the crank sensor siganl and then sends an rpm siganl to the ecm to fire the injectors off. If you have no pulse and no spark It could be an ICM or a crank sensor. you can check that really quick with a digital ohm meter. the yellow and pruple wires going into the ICM are the wires that goto the crank sensor. measure across those 2 wires you should have between 800-1400 ohms. then switch the meter over to ac~ volts and crank the car you should see a volatge reading there maybe in the 200MV range with a good strong battery to crank it over fast. if you don't have either the crank sensor is junk!