Cam Position Sensor Help

[_qWERTY]

Hey Guys,

I'm having trouble with my Cam position sensor.

I have a '99 a4 1.8t with an AEM ems. I'm ready to start it but I have a small problem. Basically, the ems needs to sync the cam and crank before it lets the plugs and injectors fire. Everything is fine except for the CPS. I checked continuity to the ems and its good (pin 2). Ground is also good (pin 3). I don't think the sensor is getting any power. I tried following the Bentley procedure regarding the CPS and they say with the key on, you should get at least 4.5v measuring between pins 1 + 3 on the CPS connector. I get 0v. (Not sure if this is the case with this ems) Where does pin 1 connect to on the stock ecu? Does it just receive a switched +12v source? If it does, I was thinking about running a new wire to a switched 12v terminal to see if that cures my problem.

I wish I could just connect my old ecu, but the harness is custom made and totally different. I contacted the guy who made my harness and he hasn't gotten back to me yet.

Any ideas?

Thanks.



**UPDATE** sensor just needed 12v.

[jbutlertelecom]

I believe this was posted recently so I did a search and here's the link:

http://forums.vwvortex.com/showthrea...4#post77819644

It has the pin out and testing procedures right in the 1st post.

I believe the procedure is as follows: "On the sensor, pins 2-3 should read 730-1000 ohms, while pins 1-3 and pins 1-2 should read infinite ohms (no connection)"

[_qWERTY]

Thanks,

Isn't that for the sensor though? I know my sensor is good - I should have stated in the OP that I've already tried 3 different sensors. This problem is a harness issue.

[jbutlertelecom]

right, but the circuit is not energized. It's a magnet/hall sender that senses (triggers) a signal when the hole/missing metal passes by the magnet. it's a simple circuit I just thought you would be interested in the way it pins out at the connector. Three wires, signal, ground and shielded connection.
2001 AMU pins out to the following #'s: CPS resistance specs (2001 AMU):
Pin 1 = shielding (at square, keyed end of harness connector) = ECU 108
Pin 2 = ground = ECU 90
Pin 3 = signal = ECU 82
So find those in your connector/circuit diagram and patch accordingly.
I think maybe the issue is the circuit is 0-5v signal?
Pin #2 is ground, Pin #3 is signal so that is where resistance would be found at the harness end. Pin 1 is a shielded no signal connection (shielding around the cable for EMI interference).
So according to your schematic you would have White (common ground) as your ground to Pin #2 CPS, Green (mag) or Black (hall) on harness goes to Pin #3 (signal) on CPS and Shield to Pin #1 on CPS.

I don't think you need a 12v connection as according to the schematic that red wire is a power source from the EMS (for use with a cam sensor that requires a power source) ours do not require power (simple magnetic sensor) so use the green wire (Pin #21 on the EMS harness, magnetic type) for the trigger instead of black (hall type).
Good luck

[Charlie_M]

I believe this was posted recently so I did a search and here's the link:

http://forums.vwvortex.com/showthrea...4#post77819644

It has the pin out and testing procedures right in the 1st post.

I believe the procedure is as follows: "On the sensor, pins 2-3 should read 730-1000 ohms, while pins 1-3 and pins 1-2 should read infinite ohms (no connection)"

No, those are the specs for the *crank* position sensor. Groggory took them from my post (here: http://forums.vwvortex.com/showthrea...1#post75688707) and thought it was for the *cam* position sensor when he put it in the FAQ. Sorry for the confusion, I never noticed the error in his FAQ. I'll reply in his thread too.

[Charlie_M]

Hey Guys,

I'm having trouble with my Cam position sensor.

I have a '99 a4 1.8t with an AEM ems. I'm ready to start it but I have a small problem. Basically, the ems needs to sync the cam and crank before it lets the plugs and injectors fire. Everything is fine except for the CPS. I've tried 3 different sensors, so I think it's a harness issue. I checked continuity to the ems and its good (pin 2). Ground is also good (pin 3). I don't think the sensor is getting any power. I tried following the Bentley procedure regarding the CPS and they say with the key on, you should get at least 4.5v measuring between pins 1 + 3 on the CPS connector. I get 0v. (Not sure if this is the case with this ems) Where does pin 1 connect to on the stock ecu? Does it just receive a switched +12v source? If it does, I was thinking about running a new wire to a switched 12v terminal to see if that cures my problem.

I wish I could just connect my old ecu, but the harness is custom made and totally different. I contacted the guy who made my harness and he hasn't gotten back to me yet.

Any ideas?

Thanks.

Here is a picture of the harness. Pin 24 on the ecu connector is for the cam.

I don't know anything about AEM systems, but looking at the schematic you posted it seems like their ECU could use either a hall effect sensor or inductive sensor. IE, cam sensor input to ECU would be pin 21 for inductive, or pin 24 for a hall. Similarly, inductive crank input would be pin 22 or pin 25 for hall. Inductive sensors are also known as VR or variable reluctance.

Stock 1.8T crank sensor is inductive: 2 signal leads and a shield, no power needed. Stock 1.8T cam sensor is hall effect, signal, power and ground leads. I think the cam sensor takes 5V, not full 12V. So definitely don't run 12V directly to it (in fact it should be there already, in the red wire, just not hooked up). Instead, I *think* you take the 5v power for the cam sensor from pin 23 on your ECU (labeled "VSS Hall").

Probably best to get some guidance from AEM or somebody who has put an AEM on a 1.8T.

[jbutlertelecom]

I don't know anything about AEM systems, but looking at the schematic you posted it seems like their ECU could use either a hall effect sensor or inductive sensor. IE, cam sensor input to ECU would be pin 21 for inductive, or pin 24 for a hall. Similarly, inductive crank input would be pin 22 or pin 25 for hall. Inductive sensors are also known as VR or variable reluctance.

Stock 1.8T crank sensor is inductive: 2 signal leads and a shield, no power needed. Stock 1.8T cam sensor is hall effect, signal, power and ground leads. I think the cam sensor takes 5V, not full 12V. So definitely don't run 12V directly to it (in fact it should be there already, in the red wire, just not hooked up). Instead, I *think* you take the 5v power for the cam sensor from pin 23 on your ECU (labeled "VSS Hall").

Probably best to get some guidance from AEM or somebody who has put an AEM on a 1.8T.

Thank you for clarifying this. I had it backwards too (like grog's post, was using it as a reference, anyway). I'm not at work so I couldn't look it up. (sorry if I was misleading you there )
Nice work CharlieM, it is actually a pretty simple circuit if you know those two pieces.
Now go get that beast running!

[_qWERTY]

I don't know anything about AEM systems, but looking at the schematic you posted it seems like their ECU could use either a hall effect sensor or inductive sensor. IE, cam sensor input to ECU would be pin 21 for inductive, or pin 24 for a hall. Similarly, inductive crank input would be pin 22 or pin 25 for hall. Inductive sensors are also known as VR or variable reluctance.

Stock 1.8T crank sensor is inductive: 2 signal leads and a shield, no power needed. Stock 1.8T cam sensor is hall effect, signal, power and ground leads. I think the cam sensor takes 5V, not full 12V. So definitely don't run 12V directly to it (in fact it should be there already, in the red wire, just not hooked up). Instead, I *think* you take the 5v power for the cam sensor from pin 23 on your ECU (labeled "VSS Hall").

Probably best to get some guidance from AEM or somebody who has put an AEM on a 1.8T.

Thanks Charlie - the guy who made my harness had it on his a4. He's just sooooo slow to get back to me...He did say something about the VSS though. I guess that's what I'll check the next time I'm at the shop.

I wanna get this thing going!

**Update

Sensor needed 12v and it synced in seconds.

Sadly, going in a different direction and don't need this ems/harness - vrt anyone?