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Pulling hair out - Need exact answer on ls9 cam swap
Hello, I have a new turbo 5.3 build, running the Holley HP system with LS1 harness 550-602N. 24x reluctor and 1x cam sprocket. I'm running an ls9 camshaft, and hence had to install an LS2 front cover with front cam sensor (part number 12591720).
Engine won't run and datalogs show no cam signal at all, or sometimes erratic/sporadic signal. I've been researching for days and can't find a straight answer on how to make this work.
1. Some say the front cam sensor will work fine.
2. Some say the 2 outer wires on cam sensor harness must be swapped.
3. A post on MSD's site says 2 outer wires must be swapped, with a 1K 1/2 watt resistor bridged across them.
4. Holley rep says their LS1 harness sends +12v signal to cam and crank sensors while their LS2 harness (with front cam sensor) sends +5v signal to cam and crank sensors.
Does anyone know EXACTLY what needs to be done to make the front cam sensor work with a Holley HP ECU??? Any help would be MUCH appreciated.
I did a ls9 cam swap but i had the stock pcm, however i think this should work the same way. Looks like you have everything else covered, just swap the 2 outer wires on the plug. I just cut and joined the 2 wires but maybe because you have the Holley ecu, you will need a resistor. But i would first just swap out the wires and see what it does.
Sounds like you need to do the wire swap and or the bridge resistor. First, I'd check to see what the reference voltage being fed by the ECU is. Measure at the cam sensors connector. Make sure the sensor runs on that. From what I remember the LS1 harness is 5v grey wire from PCM. If the Holley is pumping out 12v and expecting to be on the sensor at the back of the motor, you'd need to bring that down as the sensor on the front wants 5v. Hopefully the sensor is still good.
I think that's the smallest intercooler I've ever seen on a v8. :-) back pressure will be really high. Beautiful engine bay though. Have you considered A2W? A core between the rad and engine with a big exchanger in front of the rad? Would be heavier but WAY better than the A2A you have now.
Sounds like you need to do the wire swap and or the bridge resistor. First, I'd check to see what the reference voltage being fed by the ECU is. Measure at the cam sensors connector. Make sure the sensor runs on that. From what I remember the LS1 harness is 5v grey wire from PCM. If the Holley is pumping out 12v and expecting to be on the sensor at the back of the motor, you'd need to bring that down as the sensor on the front wants 5v. Hopefully the sensor is still good.
Yeah this is what I can't find solid information on. Lots of people mention just swapping the outer wires and it works fine with their LS1 harness/PCM. So is it really a 5v sensor only.....or does it work with either 12 or 5v? If fed with 12v...maybe it returns a 12v signal, and if fed with 5v it returns a 5v signal?
Anyway, I did test the plug and its being fed 12v from the holley PCM. I'll try swapping the outer wires and see what it does.
As for the intercooler, yeah I know. Its a Corvette and space is really limited. My original plan was A2W but had no space, so I contemplated no intercooler at all. Then I found a cheap ebay unit that would squeeze in front, so I figured better than nothing. Its just a lower-hp build. Wife's street cruiser, so it should be fine.
Sensors are 5 or 12. Not both. I'd check on the pn of the sensor. If it's 5v you need to drop that voltage down with a resistor across the 12v and gnd.
I think you could fit an a2w in there. Doesn't need to be big, just a lot more than what you have. My biggest concern would be the pressure drop forcing the turbo to work harder and thus reducing the overall efficiency of the system as a whole. I'm sure it's better than nothing at 5lb but that turbo would normally push a lot more air at 5lb than a 16g would at 5lb.
Sensors are 5 or 12. Not both. I'd check on the pn of the sensor. If it's 5v you need to drop that voltage down with a resistor across the 12v and gnd.
I think you could fit an a2w in there. Doesn't need to be big, just a lot more than what you have. My biggest concern would be the pressure drop forcing the turbo to work harder and thus reducing the overall efficiency of the system as a whole. I'm sure it's better than nothing at 5lb but that turbo would normally push a lot more air at 5lb than a 16g would at 5lb.
Well, I'll make you a deal. If we can just get the dang engine to run....then I promise to re-evaluate the intercooler situation! hahaaa..
Amazing how this would seem like the simplest thing. Stupid cam sensor. I don't know how so many people post about just swapping the 2 outer wires with no mention about 5v versus 12v. I'd like to hear from anyone who has actually done the swap, ESPECIALLY with a Holley ECU.
The issue lies with using a harness designed for an LS1 sensor obviously. Swapping wires, unless they are just a different pinout between ls1 and 2 is simple. But when you only have three wires, gnd, 12v and a square wave from the hall sensor, swapping will only fix incorrect pin outs.
Looking up that sensor, it looks like it's supposed to be a 12v power source. hopefully it's just a pin out error.
The issue lies with using a harness designed for an LS1 sensor obviously. Swapping wires, unless they are just a different pinout between ls1 and 2 is simple. But when you only have three wires, gnd, 12v and a square wave from the hall sensor, swapping will only fix incorrect pin outs.
Looking up that sensor, it looks like it's supposed to be a 12v power source. hopefully it's just a pin out error.
Well I found 2 bits of info in other posts:
I looked into the sensor at the pins. Above Pin A was a "+", above Pin B was a "-", and above Pin C was an "o". WHAT??????? It hits me then that GM in their infant wisdom screwed me. Apparently, Cam Sensor pin out is correct, ONLY if you have the factory intermediate Cam sensor harness. It seems GM used the factory intermediate harness to swap the wires on Pin A and Pin C. If you don't use the intermediate harness and plug the sesnor connector directly into the sensor (like I do), then Power needs to be supplied to Pin A and the signal should be on Pin C.
And on Holley forum:
For the cam sensor, if you have a 1x cam wheel, you need the dark colored sensor, and it needs to see 12V.
If you have a 4x cam wheel, you need the whitish colored sensor...and it needs 5V.
They are not interchangeable.
You can not use a whitish sensor with a 1x wheel, and you cannot use a dark colored sensor with a 4x wheel.
Make sure you have the correct cover and sensor to go with your cam wheel.
....And from another member:
I've used the tan 4x cam sensor on 400 motors with 1x cam gear, so I have no clue why this info being put out there. I just
did it on one this week. Then again, I've also been using 12 volts on grey 58x crank sensors since 2006, and that's a no go
With all that info collected I think you should have that car running by now! By the way, that is one sweet looking engine compartment.
Thanks! Yeah I think I have it solved. Didn't have time to finish it up last night, but I will tonite. I'll post up the correct info once I'm done, to help others. Its unbelievable how much mis-information is posted everywhere about this particular issue.
any update ?? Ive been following your thread here and on holley. Im doing the exact same thing in my car. Im just waiting on you to figure it out. lol.. I know with all the research youve done you will get it right!
any update ?? Ive been following your thread here and on holley. Im doing the exact same thing in my car. Im just waiting on you to figure it out. lol.. I know with all the research youve done you will get it right!
Oh yeah, sorry for not updating this thread. The answer is really simple, its unbelievable how much MIS-information people post about this.
Cam and crank sensors have a built-in, internal voltage regulator specifically so they can be used with a variety of input voltage signals. GM uses the same cam sensor with both 5v and 12v signals, depending on application. So that question is SOLVED, once and for all.
To use the LS2 sensor, you just need to feed it input voltage on pin A. The pins are labeled right on the plastic connector if you look closely.
LS2 harness feeds power to Pin A.
LS1 harness feeds power to Pin C.
So if you want to use an LS1 harness, you just need to swap the 2 outer wires (pins A & C). Thats all I did, and mine fired right up.
I should note, if you're using a holley ECU, you can't just pick 24x from the ignition dropdown when using an LS2 sensor.
You have to select "custom", then fill in the settings.
Holley rep told me this:
Type: Lsx 24 tooth
Inductive delay: 1.0usec (not sure this is correct...I've seen various answers)
Timing Offset: 0
Cam sensor: 1x
Output setup: DIS Coil on Plug
Dwell time: 5.0msec (not sure this is correct...I think it should be 4.5)
Also not sure if it should be digital rising, or digital falling. I've read it should be "rising", but I've also seen posts from Danny that it should be "falling".
Maybe others can chime in here.
06-14-2015, 09:45 PM
Pulling hair out - Need exact answer on ls9 cam swap 
