2003 trailblazer V8 5.3L tacch wire?

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=16685
Printed Date: July 15, 2025 at 2:57 PM

Topic: 2003 trailblazer V8 5.3L tacch wire?

Posted By: armperez01
Subject: 2003 trailblazer V8 5.3L tacch wire?
Date Posted: July 25, 2003 at 7:24 AM

I cannot get this aps-996 to learn a tach. I've tried the uncommon injetor, uncommon igniter, tach behind inst. cluster. all notes I have are for inline 6. Help a frustrated tech.....

Replies:

Posted By: draasch
Date Posted: July 25, 2003 at 7:53 AM

Remote Start
Tach Signal WHITE AT PCM * #238
Ignition #2 WHITE IGNITION SWITCH HARNESS
Ignition #3 ORANGE IGNITION SWITCH HARNESS
Accessory BROWN IGNITION SWITCH HARNESS
Neutral Safety WHITE (-) PCM CONN C3 PIN #13 *
Brake Light WHITE (+) AT SWITCH ABOVE BRAKE PEDAL
Reverse Light LIGHT GREEN (+) EITHER TAIL LT ASSY OR TRAILER CONN
Rear Window Defrost DATA CONTROLED

*PCM Located On The Drivers Side Of The Motor. Tach Wire Is In The BLUE Conn (C1) Closest To The Firewall,Pin #49. Also Found Back Of Cluster in 24 pin GREY Conn Pin # A12 #238-See G.M.Passlock II Bypass Diagram

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Good Luck
David
Ace Security
813-376-9778
Tampa
Donate to the 12volt

Posted By: armperez01
Date Posted: July 25, 2003 at 7:58 AM

draasch - are you sure these are the proper notes, they look to be the notes for the inline 6 and not the V8, in regaurds to the tach wire...

Posted By: draasch
Date Posted: July 25, 2003 at 8:35 AM

just double checked. if you look above the brake pedal, you should see a yellow connector. right below that is a large harness. inside that harness you should find a white wire that is for your brake lights and one for the tach.

TEST WITH A METER!

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Good Luck
David
Ace Security
813-376-9778
Tampa
Donate to the 12volt

Posted By: armperez01
Date Posted: July 25, 2003 at 9:03 AM

I look and looked again. The only harness above the brake is the one connected to the brake. Above that is a welded steal support for the steering column. Remember this is a V8 which the wiring for the engine and its components are different from the inline-6. There has to be someone that has done a 2003 V8 version....Please......

Posted By: Chris Luongo
Date Posted: July 25, 2003 at 4:30 PM

I haven't done a V8. But the large harness draasch mentions is about 1.5" thick, and you can see it coming right in from the firewall. Tach is the first thin white wire you see in there. Also, there's a very light gray that's not tach, so use a good light when looking. Again, though, not sure if any of this will apply with the 8.

Also, though, the Trailblazer will work just fine tachless. If you haven't noticed, it's impossible to under-crank or over-crank the engine---go ahead and try it with your key. Just tap it to Start; the engine starts perfectly. Or hold it in Start all day and nothing will happen. So you can get by pretty good with voltage sense.

The only downside to using voltage sense with Audiovox is that "pit-stop" mode will no longer work. That's the mode where you park your car, engage the remote start, then remove your key and the engine stays on.