Help Problems with 402cid Cam positioning sensor "CPS" harness , not reading RPMS !!
06-17-2008, 02:28 PM
#1
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Mar 2006
Location: Columbus , Ohio
Posts: 392
Likes: 0
Received 0 Likes
on
0 Posts
Help Problems with 402cid Cam positioning sensor "CPS" harness , not reading RPMS !! I got my 402cid installed and everything hooked up with all fluids topped off and went to go start up the engine and the Tach is not reading RPMS at all , i switched the 2 end wires on the wiring harness and its still not working correctly , its a Katech CAm positioning Sensor harness with the 2 knock sensors , what could be wrong here ? nothing as far as the rpms are working , and i know thats what makes it hard to fire up on start up is the Cam sensor not reading is there a fuse or somthing for this ? i know my harness is correct i just dont understand anything .. what can i do here ?
06-17-2008, 05:22 PM
#3
I would try swapping the wires and trying it. Typically that is the problem. If that doesn't work, ohm out both harnesses and make sure there isn't a wiring problem in them. Also, look over the wiring and make sure nothing is pinched or improperly connected. If everything looks good, find a hand-held scanner and see if you are getting a crank and cam count. If not, you may try to put a new cam sensor in and try that. We have seen a little bit of everything. I would think by running through these steps you will find the problem. 
Jon
Jon
06-17-2008, 08:52 PM
#5
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Mar 2006
Location: Columbus , Ohio
Posts: 392
Likes: 0
Received 0 Likes
on
0 Posts
where could i find one of those hand held scanners at jon ?
I would try swapping the wires and trying it. Typically that is the problem. If that doesn't work, ohm out both harnesses and make sure there isn't a wiring problem in them. Also, look over the wiring and make sure nothing is pinched or improperly connected. If everything looks good, find a hand-held scanner and see if you are getting a crank and cam count. If not, you may try to put a new cam sensor in and try that. We have seen a little bit of everything. I would think by running through these steps you will find the problem.
Jon
Jon
Trending Topics
06-19-2008, 02:05 PM
#9
He was talking about the cam gear...you should have the 1x cam gear, where on the face there is a 180º raised, and the other half is flat. Then the later models have the 4x, where there are 4 raised areas for the cam sensor to read position.
__________________
Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
06-19-2008, 11:39 PM
#10
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Mar 2006
Location: Columbus , Ohio
Posts: 392
Likes: 0
Received 0 Likes
on
0 Posts
ahhh , got ya , yeah i have the Comp cams LS2 adjustable timing set Part # KT 3157 its raised on 180* of one side this should be right shouldnt it ? i just dont understand why im not getting a cam signal to my Tach , nor did it on my last LS2 Engine ..
06-20-2008, 09:17 AM
#11
Is this the second motor with that chain that hasn't had a signal? You might try putting on a GM LS2 T-chain set and just see if that fixes problem. I know it's a pain pulling it all back apart but that may be the problem right there. Two motors, same chain, same problem... Something to look at.
Jon
Jon
06-20-2008, 03:57 PM
#12
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Mar 2006
Location: Columbus , Ohio
Posts: 392
Likes: 0
Received 0 Likes
on
0 Posts
Is this the second motor with that chain that hasn't had a signal? You might try putting on a GM LS2 T-chain set and just see if that fixes problem. I know it's a pain pulling it all back apart but that may be the problem right there. Two motors, same chain, same problem... Something to look at.
Jon
Jon
The last motor i had was just the LS2 364cid with the stock GM LS2 timing chain and set , but this 402cid stroker motor i put the Comp cams Adjustable LS2 timing set in Part # 3157KT and its still not working , thats what confuses me ..
06-20-2008, 08:56 PM
#13
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Mar 2006
Location: Columbus , Ohio
Posts: 392
Likes: 0
Received 0 Likes
on
0 Posts
i checked all the wire and im not getting 12v to the CPS but I have 12v at the pcm at connector 39, but not at the sensor. I hooked a wire up to the red wire on the sensor which comes out of connector 39 at pcm, and it still didnt work?? any ideas
06-20-2008, 10:42 PM
#14
10 Second Club
iTrader: (15)
Join Date: Nov 2001
Location: St. Michael, MN.
Posts: 4,519
Likes: 0
Received 0 Likes
on
0 Posts
Do you have 12v (red wire) at the PCM side of the OEM connector? If so, and you do not the have 12v to the cam sensor itself, the wiring is crossed somewhere in between. For the LS1, each wire on the female connector is marked as follows; B-Pink/Black (Reference/ground) , A-Brown/White (CMP signal input) and C-Red (12v received from the PCM). It sounds like the two outer wires are crossed. The Katech harness swaps the outer two so it should work, but either way verify the actual wiring by tracing the 12v from the PCM through each connection, down to the cam sensor to find the disconnect. It's really easier than it sounds.
06-21-2008, 12:50 AM
#16
If swapping the wires like stated above doesn't work check this out. The 3 ground wires at the back of the head or block have to be on and grounded or the same thing will happen. Tach won't work and it will either not fire or pop and backfire. I already had this problem twice. Most of the time though you just have to swap the outside cam sensor wires and you'll be good to go!
06-22-2008, 09:33 AM
#17
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Mar 2006
Location: Columbus , Ohio
Posts: 392
Likes: 0
Received 0 Likes
on
0 Posts
Do you have 12v (red wire) at the PCM side of the OEM connector? If so, and you do not the have 12v to the cam sensor itself, the wiring is crossed somewhere in between. For the LS1, each wire on the female connector is marked as follows; B-Pink/Black (Reference/ground) , A-Brown/White (CMP signal input) and C-Red (12v received from the PCM). It sounds like the two outer wires are crossed. The Katech harness swaps the outer two so it should work, but either way verify the actual wiring by tracing the 12v from the PCM through each connection, down to the cam sensor to find the disconnect. It's really easier than it sounds.
We used a meter and checked for continuity on connector 39 and touched it to all 3 spots on the Cam positioning sensor wiring that comes out of the PCM and it didnt beep once
so i just need to take it somewhere ..
But here at the Same point when my buddy Clears codes out of the PCM with his Snapon Scanner the Tack starts Reading for a Quick Second then just goes back to zero.. Plus his Snap on Scanner is Reading RPM's From the Computer but the Tacks not thats whats not making sence here ..
06-22-2008, 11:38 AM
#18
10 Second Club
iTrader: (15)
Join Date: Nov 2001
Location: St. Michael, MN.
Posts: 4,519
Likes: 0
Received 0 Likes
on
0 Posts
1) -We used a meter and checked for continuity on connector 39 and touched it to all 3 spots on the Cam positioning sensor wiring that comes out of the PCM and it didnt beep once
so i just need to take it somewhere ..
But here at the Same point when my buddy Clears codes out of the PCM with his Snapon Scanner the Tach starts Reading for a Quick Second then just oes back to zero.. 2) -Plus his Snap on Scanner is Reading RPM's from the Computer but the Tach not thats whats not making sense here ..
so i just need to take it somewhere ..
But here at the Same point when my buddy Clears codes out of the PCM with his Snapon Scanner the Tach starts Reading for a Quick Second then just oes back to zero.. 2) -Plus his Snap on Scanner is Reading RPM's from the Computer but the Tach not thats whats not making sense here ..
1. Let me make sure I have this correct; With the ignition ON (engine off), you have 12v on PCM PIN #39 (PCM Connector C2 Color Red), but not at the PCM side of the original (not the cam sensor or aftermarket harness) harness connector (located right by the MAP sensor connector)?
IF yes, the wire in between the PCM and connector is broken or shorted.
2. Does the rpm's actually match the engine revving; or is stuck high or low?
Does the tachometer gauge sweep from low RPMs to high RPMs and return to low RPMs? You may have a bad instrument cluster, but that's a different process altogether.
3. Please take a picture of the connector where there is no voltage and post it.
You have to be patient when chasing automotive electrical gremlins especially when dealing with a system this complicated. Taking the car to a professional will usually cost $100/hr or more to chase the same problem.
06-22-2008, 06:32 PM
#19
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Mar 2006
Location: Columbus , Ohio
Posts: 392
Likes: 0
Received 0 Likes
on
0 Posts
I honestly think the wires are crossed somewhere in between the PCM and the cam sensor itself, but...
1. Let me make sure I have this correct; With the ignition ON (engine off), you have 12v on PCM PIN #39 (PCM Connector C2 Color Red), but not at the PCM side of the original (not the cam sensor or aftermarket harness) harness connector (located right by the MAP sensor connector)?
IF yes, the wire in between the PCM and connector is broken or shorted.
2. Does the rpm's actually match the engine revving; or is stuck high or low?
Does the tachometer gauge sweep from low RPMs to high RPMs and return to low RPMs? You may have a bad instrument cluster, but that's a different process altogether.
3. Please take a picture of the connector where there is no voltage and post it.
You have to be patient when chasing automotive electrical gremlins especially when dealing with a system this complicated. Taking the car to a professional will usually cost $100/hr or more to chase the same problem.
1. Let me make sure I have this correct; With the ignition ON (engine off), you have 12v on PCM PIN #39 (PCM Connector C2 Color Red), but not at the PCM side of the original (not the cam sensor or aftermarket harness) harness connector (located right by the MAP sensor connector)?
IF yes, the wire in between the PCM and connector is broken or shorted.
2. Does the rpm's actually match the engine revving; or is stuck high or low?
Does the tachometer gauge sweep from low RPMs to high RPMs and return to low RPMs? You may have a bad instrument cluster, but that's a different process altogether.
3. Please take a picture of the connector where there is no voltage and post it.
You have to be patient when chasing automotive electrical gremlins especially when dealing with a system this complicated. Taking the car to a professional will usually cost $100/hr or more to chase the same problem.
The other thing is when i had my LS1 in the car it worked , but hasnt worked with my LS2 364cid or my 402cid engine either ..
Last edited by BadLtBlu99TA; 06-22-2008 at 06:52 PM.
06-22-2008, 09:36 PM
#20
10 Second Club
iTrader: (15)
Join Date: Nov 2001
Location: St. Michael, MN.
Posts: 4,519
Likes: 0
Received 0 Likes
on
0 Posts
Correct me if I'm wrong, but the first pic is the Katech harness and the second pic is the lower connector on the front cover. If so, you're testing the wrong connectors. You need to completely disconnect and remove the Katech harness and test the OEM/original connector located by the firewall.
Here is a crude diagram that should help pinpoint the issue.
Here is a crude diagram that should help pinpoint the issue.