Hello all,

I've been having an intermittent no-start issue (in the rain or over wet ground being the common factor) with my Blazer for several months now. I replaced the cap and rotor without success, then changed the crank position sensor and the problem disappeared completely...for a while anyway. After the 5th or so driving rain storm, the no-start problem came back, so I went ahead and replaced the ignition control module. After replacing this, I tried to again start it during a hard rain storm, and though it took some effort, I got it started and finally got it to throw a code - P1351 (Ignition Coil 1-4 Control Circuit High Input). I checked under the hood for any loose connections and found that the Black connection to the VCM was loose, although it appears that this particular connection doesn't have anything to do with the ignition system. The rest of the connectors look good and feel solid, sprayed it down at night and couldn't find any arcing (nor did dousing ignition system and VCM region with a spray bottle cause a no-start condition after waiting 30 minutes...in other words, I couldn't replicate the condition). I'm going to do the tests as specified on the P1351 page with a digital multimeter and a continuity tester whenever it stops raining, but in the mean time, does anyone have any additional thoughts or suggestions? Would any wires aside from the white wire from the VCM to the ignition control module cause the high input voltage code? I'm hoping it's just a wire or a connection, but I'm running out of ideas and am hesitant to replace the VCM itself unless I really have to. Thanks in advance!

 

It really is time to dig in with you DMM and ohm out the wires. Check everything that is listed in the troubleshooting chart and let us know the results.

Good luck!

 

I disconnected the injector harness connector, cranked it, and got a P1351 code showing that it's not intermittent. I then disconnected the connector to the ignition control module and probed terminal B while cranking it, which read 5.6V (well over the specified values). I then checked for an open in the circuit by checking the resistance between the VCM C3 connector pin 7 (the instruction sheet said pin 9, but pin 9 on my '99 isn't connected to anything - the white wire connects to pin 7) and terminal B on the ignition control module - as it didn't go to infinity, I assumed it wasn't an open, although I don't recall the exact value off-hand (I doubt it is the ignition control module anyhow, as I just replaced it a week ago and it hasn't made any difference). I then reconnected the VCM C3 connector, turned the ignition to on with the engine off, and checked the voltage, only to get a reading of 0 (the troubleshooting chart didn't list any value, so I'm presuming it means any value greater than 0). The next step after that is to check the connections to the VCM, which I checked for the third or fourth time and found everything to be in order, thus the next step per the troubleshooting chart is to replace the VCM. If anyone has any additional thoughts or anything, I'd love to hear them...but right now, I'm prepared to buy another VCM as soon as my next paycheck shows up.

 

Nick, did you solve the P1351 by replacing the VCM?

 

hey have same problem on my 99. found code was set due to crack in ignition coil ... also gave me code PO300 (multiple miss fire ) try replacing coil.. Can also create a failure to start at operating temp...

 

So far I went thru this twice. The first time it ended up being the pigtail connector for the coil and the second time it ended up being the ignition rotor. Both times i had problems once in a while with the truck starting up and the code poping up and finally a tow truck had to bring it back home.