07 trailblazer tach wire

I've done a little research and can't seem to find exactly where this tach wire is located. I've taken a few pictures of the plugs I'm assuming it is suppose to be in but haven't found a wire that tests out as a tach signal. According to most of the tech diagrams it is in a blug plug at the PCM, pin number 49. Says the PCM is on the drivers side of the motor. The pictures I've uploaded are the modules on the drivers side of the motor, however the initial blug plug I found is only a 48 pin harness, 4rows x 12 columns. There were two white wires in this bunch I tested just to be sure and nothing came out as a tach signal. There is a bigger module that I believe is the actual vehicle computer, but it has 3 harnesses plugged into it, all have black handles, but if I look really close, there is a harness that has a blug strip right at the base of where it plugs in at. I found a couple white wires in that one harness but again they don't test as tach wires. Any thoughts? I'm to the frustrated point now. I'm installing a viper 5901 in a 2007 Chevy Trailblazer SS and it remote starts fine when in virtual tach or voltage sense mode, but after about 15 seconds the engine shutsdown and cycles through this 3 times before shutting off. I checked the remote start shutdown history and its saying its shutting down due to low voltage. Everything is testing at 12V or higher even during start and after start. I figured I'd try finding the tach wire and going with a tach signal since that is the most accurate way to do it. Now if I could only find that tach wire!

pull the gauge cluster, it's the only white wire thereAdvanced

Thanks for the info. Unfortunately I already tapped onto the fuel injector wire. I'll be taking the dash apart to hookup my stereo turn-on and I'll check for the white wire you're talking about. I'd rather get the tach inside that cab than have another wire under the hood. Thanks again for the tip!

If anyone cares to know where I attached my tach wire here are some photos. If you look for the 2 wire injector connector one of the wires has tach signal. Usually if you look at multiple tach connectors the wires usually have one of the same color and one that is different from the other injectors. The different color wire usually holds the tach signal. Photo Link

I grabbed the white wire at the cluster as well, lots of room to connect it

groundzero2010 wrote: Everything is testing at 12V or higher even during start and after start. I figured I'd try finding the tach wire and going with a tach signal since that is the most accurate way to do it. Now if I could only find that tach wire!

When you test a tach wire, your meter needs to be set to AC volts not DC volts. It should test around 2-4 volts and fluctuate when you rev the engine.

did you hook up 2nd Acc?  you have to on the 05-up TB's.....Kevin Gerry

Certified Electronics Technician

MECP First Class Installer

Owner/Installer

Classic Car Audio

since 1979

kgerry wrote: did you hook up 2nd Acc?  you have to on the 05-up TB's.....

What doesn't work if you don't hook up 2nd Accessory?