2001 blazer transmission/speedo/everything problem
 

Hi guys. I am a first time poster, and I seriously need some help to keep from going insane.

I bought a 2001 blazer 4.3, 4l60-e, 154k for a dealer back lot last week. Bought it with a bad transmission. No 1st gear, no 4th gear. Starts out in 3rd gear if left in D, but will start in 2nd if shifter is pulled down to 1 or 2 selection. No speedometer. ABS, "brake", and check engine light on. (check engine light is on VERY VERY DIM almost cant see it dim).

No worries right. I have an 01 blazer rolled over with a donor trans and speed sensor. I drove it, ran it everything works on it, except the computer was taken back by the guy i bought it from after i tested it all, but that is beside the point.

I put the trans it today, and everything went so smooth, waaaayy too smooth. I mean this baby went in like butter. Button her up, with the new trans, new speed sensor and guess what.....No 1st gear, no 4th gear, no speedo, everything that was wrong before is still wrong.

I have access to a Gm Tech 2 scan tool (dont ask). I am getting codes for: MIL circuit fault ( explains why the SES light is on real dim?) No speed sensor curcuit 2 output, 1-2 shift solenoid fail, 2-3 shift solenoid fail. BUT. When i drive it i can look on the readout of the tech 2 and see i am getting speed sensor signal. I can use the tech 2 and activate the speedometer in the cluster. I can clear all the codes and they come right back. I am stumped for the moment. I have switched clusters and Body control modules with known good ones to no avail. I have wiggled wires, checked every ground I know how, and still can not find anything out of place out of the ordinary. Engine runs awesome, not a skipped beat. I know 4l60-e's only have 2 and 3 when they lose electrical (computer) control. Possible i have a bad ecm?

Has anyone had any or all of these anomolies at once?? I dont know if all of the problems are intertwined with each other, or am i dealing with seperate issues?

Please help, any ideas at all that will help this poor soul look somewhere that he is overlooking or give my brain a jumpstart will be hightly appreciated
Thank you

Bill

What were the actual codes?
P0751 - Shift Solenoid A Performance or Stuck Off
P0753 - Shift Solenoid A Electrical
P0756 - Shift Solenoid B Performance or Stuck Off
P0758 - Shift Solenoid B Electrical

Have you checked the CLSTR fuse? If that is ok, have you monitored the IGN 0 wire (feed to the CLSTR fuse) to see if the voltage drops out? This condition can be caused by a failing ignition switch.

Ok, So yesterday i looked at your diagrams. I also went to alldata and pulled up some diagrams and tests. 1st code was for MIL circuit being bad. I did the test, and the circuit passed, the fix was to replace ecm. We changed iggy switches and still nothing. The common thread we are finding with every code is that every system that is giving a code, the computer triggers the ground........we are certain that the ECM is faulty. I have a replacement on its way today so tonight will shine more light on the subject. Thanks again for your reply

Bill

Put in replacement ECM, fixed all of the above issues. 55$ from the wrecking yard. I wish the old trans was in it just to see if it really was too bad. Oh well. Thanks for the insight.

Bill