When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So I have a 2002 LQ9 engine (DBW) in my Firebird -68. Unfortunately the CC does not work. I have not find any post regarding the wiring for the LQ9 engine. I think that I have the right wiring. The TCC wire always hot to PCM C1 Pin 33 and Stop lamp supply to TAC C1 Pin 6. Currently I use one a switch for activate cruise control TAC C1 Pin 14 and a switch that I can toggle between set coast C1 Pin 4 and resume/accel C1 Pin 5. This toggle switch is only hot when the cruise control is activated.
One thing that is strange is that out from TAC C1 Pin 6 (stop lamp supply) I have 4.5 V (I have disconnected the wire from the brake lamp) Is this normal ? I guessed that it would be 0 V out from the TAC.
Anyone who have experience with LQ9 DBW ? As I understand it is not 100% equal with the LS6 used in the Corvette since the TB is mirrored.
As long as you have a 4 prong brake switch, it sounds like your wiring is for the most part correct, but just to be sure, you need a latching on/off switch on pin14, with power with the ignition ON. from there, you need two momentary switches, one on each of the pins 4 and 5 that provide 12v ignition power when pressed. Is this the way you have it? Your sentence "toggle between 4 and 5 " is a little confusing. also, if it's wired this way, make sure you have brake lights, the cruise WILL NOT work without them, also, if you have LED taillights, you will need to load the circuit since the LEDs don't have enough resistance for the cruise to work. If all that checks out, try adjusting your brake switch in slightly so it takes just a tad more pressure on the pedal to activate the brake lights, I've seen switches that the open and closed set of switches inside are not quite accurate enough so that just because the lights come on, the other set may not be opened.
I know this is an old thread, but I've been searching around for info about wiring the C1-33 TCC brake switch for my LQ9 and thought this is relevant:
Looking through the wiring diagrams for my 03 LQ9, the C1-33 pin should be hot when the brake is pressed. This is counter to everything i've read so far, but the schematic shows it plain as day.
Looking at a few different vehicles, it seems to vary based on the model and engine.
I dont think that schematic is correct. It shows both sets of terminals on the brake swithc to be normally open. This isn't the case. On those brake switches, one set is normally open and one set is normally closed, and they operate at the same time (shown by the dotted line connecting the switch contacts in your schematic) I have a schematic for a 2004 6.0 van that shows the switch has power until the pedal is pressed.
I dont think that schematic is correct. It shows both sets of terminals on the brake swithc to be normally open. This isn't the case. On those brake switches, one set is normally open and one set is normally closed, and they operate at the same time (shown by the dotted line connecting the switch contacts in your schematic) I have a schematic for a 2004 6.0 van that shows the switch has power until the pedal is pressed.
I am at work right now, but as soon as I get home I'll look up your 04 6.0L (1500 Savanna?) and see if my schematic jives with yours - should be interesting.
Mitchel1.
What I find strange is that I checked a few vehicles, finding that most of the LS1 wiring to be what everyone says it should be, 12v NC.
Most of the 6.0L I checked were 12v NO as the image I posted.
I'm interested to check your application - where are your schematics from?
Mine are from Mitchell on Demand. It's odd that your schematic shows the brake light wiring part of the switch ( the orange and white wires), most engine schematics won't show that. I still say that schematic is wrong though. Only the newer GenIV engines have power when the pedal is pressed, all GenIII's are power without the pedal pressed.
Mine are from Mitchell on Demand. It's odd that your schematic shows the brake light wiring part of the switch ( the orange and white wires), most engine schematics won't show that. I still say that schematic is wrong though. Only the newer GenIV engines have power when the pedal is pressed, all GenIII's are power without the pedal pressed.
What version are you running? I believe I've got v5. Will check later.
Would it be possible to get an image of what you see when checking my application? 6.0L, 2003 escalade.
I'd be curious if you see what I see....
Mine are from Mitchell on Demand. It's odd that your schematic shows the brake light wiring part of the switch ( the orange and white wires), most engine schematics won't show that. I still say that schematic is wrong though. Only the newer GenIV engines have power when the pedal is pressed, all GenIII's are power without the pedal pressed.
Well I checked out what I believe is your application - 04 GMC Savanna H1500 w/ LQ9: just as you've shown:
I'm genuinely curious if Mitchel is listing a bunch of schematics for a bunch of vehicles wrong, or if those schematics are actually correct and the signal varies vehicle to vehicle.
I have no idea what version of Mitchell it is, it's what we use at work. I will look tonight and see if ours shows the '03 like yours. I'm still saying the schematic is wrong though. They don't change from truck to van or anything like that.
As long as you have a 4 prong brake switch, it sounds like your wiring is for the most part correct, but just to be sure, you need a latching on/off switch on pin14, with power with the ignition ON. from there, you need two momentary switches, one on each of the pins 4 and 5 that provide 12v ignition power when pressed. Is this the way you have it? Your sentence "toggle between 4 and 5 " is a little confusing. also, if it's wired this way, make sure you have brake lights, the cruise WILL NOT work without them, also, if you have LED taillights, you will need to load the circuit since the LEDs don't have enough resistance for the cruise to work. If all that checks out, try adjusting your brake switch in slightly so it takes just a tad more pressure on the pedal to activate the brake lights, I've seen switches that the open and closed set of switches inside are not quite accurate enough so that just because the lights come on, the other set may not be opened.
I have led taillights do I have to instal resistors
I have led taillights do I have to instal resistors
You will need something or it will never set. I use relays because they don't get as hot as resistors. You only need one, tied directly to the cold side of the brake switch so that it gets power when the brake pedal is applied.
07-28-2014, 08:32 AM
Cruise control wiring LQ9 
