[MyRedSRX]

I am at the end of my rope with this so I am hoping someone can help me with this. My MIL light came on 2 weeks ago with code P0650 (right before I need a state inspection) shortly after starting. After about a half a mile of driving it turned itself off. After a few minutes more it started flashing. This has continued each time I driven the car since. I have gone through and checked the fuses and relays, reset the light only for it to come right back on. I have checked the PCM connections, they look fine, is there something more I can do here? Any helps, tips, tricks, procedures would be greatly appreciated. Thanks

 

[glake89]

This is what causes code 650, per the SM-

The ECM detects an open, a short to ground, or a short to voltage on the circuit that controls the MIL.

So, try wiggling the connector at the ECM and the connector to the dash (harder to get to). If it's not a poor connection, you may need to chase down a possible short to ground/voltage. We can help with that.

 

[MyRedSRX]

Thank you for the input. I have already checked the connection at the PCM and it was solid. I checked the instrument cluster last night after your post. It to was a solid connection and did not feel loose at all. I have a DMM but not sure where to start chasing down shorts. Any help would be greatly appreciated. Thank you again.

 

[glake89]

for starters, the MIL control circuit is a BN/WT wire at the IP connector and at the ECM connector. Disconnect both connectors and test if wire is shorted to ground. If not, turn ign. on, engine off and test again and then test for voltage. Now I've got a foot and a half snow to clean up on a 1/2 mi driveway, then I'll check back.

 

[MyRedSRX]

Thanks for the start, I will not be able to do it for a few hours (still at work) but I will report back. I would not think the light would come on at all or flicker if I was shorted to ground (I also know I may be dead wrong). I would assume if the voltage is different at the IP than at the PCM I would have to replace one of those components depending on which one has the proper voltage. In that case I hope for the IP (although being wrong about the short and replacing a wire would be awesome) otherwise I have to go to the dealer because they have to program a new PCM. Thanks again, a lot, for the insight.

 

[Cadillac Customer Service]

MyRedSRX, I'm looking forward to your updates! It's great that the community could help you out with your DIY troubleshooting, and please email me anytime if you decide to involve your dealer and would like further assistance. (I'm reachable via email at [email protected]!)

Best,

Katie
Cadillac Customer Service

 

[MyRedSRX]

Very appreciated Katie, thank you. The dealer I have dealt with in the past has always been very good so I don't anticipate a problem there if it gets to that point.

 

[glake89]

The way the circuit works is there is always (with key on) power to the MIL light. When called for, the ECM internally grounds the circuit via the BN/WT wire, turning on the lamp.

 

[MyRedSRX]

I tested for the short to no avail. Turned the key on and dramatic voltage difference between IP and PCM. Almost nothing at the PCM, I am thinking thats where my problem lies. Any thoughts? Thanks.

 

[glake89]

Did you test for short with both connectors disconnected, therefore only testing the wire?

What terminals (or wire color) did you test for voltage and were the connectors attached or still disconnected? What voltage did you get and where?

 

[MyRedSRX]

Yes, I tested for the short with both wires disconnected. I tested for voltage with the connections in place. I got 0.3 V at the PCM and 11 V at the IP.

 

[glake89]

It sounds like a short to voltage. Here are 2 tests. First, check for voltage in the wire with both connectors disconnected.
Second, make up a 3A fused jumper wire. With only the ECM connector disconnected, connect the jumper to the wire and the ECM case, then turn on ign. Does the mil. light or fuse blow?

Note: the way you tested you got feed through from the indicator lamp.

 

[MyRedSRX]

Glake89, thanks for more ideas man. I can't tell you enough how much this helps. I will try this as well. Do you mean "Does the MIL light up or does the fuse blow". I am slightly confused by the last statement but I am assuming that is what you mean.

 

[glake89]

Either one could happen.