I first posted this prioblem 2 years ago..still chasing it!!! I have been chasing this problem for 5 years total! I live in Chicago and every winter for the past 3-4 years I will experience a period of time when my engine will lose power. It always seems to start after/during a good snow... I will be driving..the truck will be running fine, then the tach will start to jerk toward 0 RPMs..almost like something is shorting..followed shortly afterward by a loss of power and the Check Engine light. The code is always the same..213 SPOUT or SAW signal open or shorted..the truck does not die..just feels like no compression or gas..can't get above 45MPH's..also sometimes the tach will be resting at 0 RPM's..but the truck running smoothly..sometimes the truck bucks and surges..almost invariatbely if I come to a stop...the truck will idle very roughly for a second..and then I will feel the engine "kick in" and the tach goes normal and it will run smoothly..after I start again..the problem will usually reappear (but not always!)....I can almost always clear up the problem by jiggling the wiring harnesses in between the power distrubution box and the firewall..(also I sometimes the tach will be at 0 RPMS's and when I jiggle the harness it jumps to normal)..and then truck will run fine..sometimes for several hundred miles!..before reappearing..and usually runs all spring/summer/fall ok...but this fall it is starting to do it..even in dry weather...I can never seem to instigate the problem on my own to troubleshoot it..I can jiggle the wiring harness..spray water all over the wires..and I can NEVER get the problem to start!..I am assuming it is some sort of intermittent ground or short..the ony real clue I have is that the problem always manifests itself with erratic jerking of the Tach..either just before the problem sytarts..or during it..and the fact that the tach can sit at 0 RPMS's with the truck running fine...


Any ideas???? I would really appreciate the tach signal path/tach gnd path if anyone knows it so I might be able to look at specific wires!!

Thanks!

 

Your problem is really strange.you say when you wiggle the PCM harness, I believe thats what your talking about,It goes normal? then it might be your pcm (power control module or brain of your truck) reacting to the cold maybe or the connection.If the computer would even do that, I have no clue or maybe its your mass air flow sensor(maf) acting up. But I dont think this would make your tach mess up when your engine is running fine. I just know that if your maf sensor goes bad your truck will smoke and run really really bad and not even idle.This may not help to much but hopefully you can some how resolve the problem.Good luck!

 

Thanks for the response..I found the problem finally!! It was a shorted IDM line (the line that runs from the ECM to the PCM to tell the PCM that the SAW/SPOUT signal was received by the ECM and thus the coils fired..it also provides TACH signal to tachometer)..it was pinched between the battery tray and the firewall..over time chaffing due to normal vibration caused the harness to wear through..and then the battery tray began cutting into the IDM line..which cause an occasional short through the battery tray to GND..this explains why I could clear it up by wiggling the harness..and why moisture seemed to exasperate the problem..because water/condensation would collect on the harness and sometimes provide a path to the tray(and thus GND) even when it was not physically touching..I suspect the loss of pwer was due to the fact that the PCM did not see the IDM signal, thus assuming the SAW/SPOUT signal was not received by the ECM and either over compensated by trying to fire more..thus messing the timing up..or not signaling the injectors to deliver gas..I'm not sure on this point...anybody know?


Thanks to All!