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-   -   04 Monte keeps stalling (https://montecarloforum.com/forum/new-member-area-4/04-monte-keeps-stalling-58947/)

N_robertson 10-09-2017 11:07 PM

Has anyone attempted bypassing the passlock system in their Monte? If so, are there any drawbacks in doing so?

plumbob 10-10-2017 10:16 AM

The resistor doesn't really bypass the passlock system, it just replaces the resistor in the lock cylinder that you already replaced, so unless that resistor is defective you'll still need to find the real problem. There's videos on Youtube that explain how to do it if you insist. Personally, I would fix the real problem. Seems like hacking up the harness just causes problems later down the road.
The steady security light is a indicator of a breach in the class 2 serial data circuit causing a "fail" to set for the CTD (content theft deterrent) system. The circuit needs to be complete in order for the PCM and BCM to enable the fuel pump and crank relay.
There should be a code. Either the scanner you're using is not smart enough to communicate with the serial data link or there's a problem with the DLC, specifically terminals 2, 5 of the DLC or terminal " A" of the splice pack, any of which would not set a DTC. You might need to get scanned with a Tech 2 which is capable of bi-directional communication and can test individual modules in the circuit as commanded by the scan tool.

N_robertson 10-10-2017 10:47 AM

So, how should I go about this? Should I tow the car to a shop to have them check for codes with a better scanner? Also, what would need to be done to "fix" the class 2 serial circuit? Thanks.

plumbob 10-10-2017 12:41 PM

Unless you find someone willing to come to you to scan I guess you'll have to get a tow. Make sure it's a Tech 2, or one like a Snap-on that can emulate a Tech 2. If you do have to get it towed, I would take it to a chevy dealer or auto-electric shop with the right scanner.
As for the fix, that depends on what the scan reveals and points you in the right direction. Could be a short, bad ground, bad connection or module.
BTW...does the car happen to have a aftermarket stereo? They can be a problem too.

N_robertson 10-10-2017 02:44 PM

Thinking that the Chevy dealer 2 miles from my house will probably be my best bet... The car does have another stock stereo in it from an impala... Although, the car was already having this issue before I swapped the stereo...

The_Maniac 10-10-2017 10:04 PM

Given what I know about the data system in these cars, it's very simple. Literally it is just wires from each computer in the car getting "spliced" together. There may be a better way to do this, but what I would try is disconnect the battery, remove the PCM, set your volt meter to do an ohms test (which can be a simple continuity test). See if you can get continuity from the data pin in the diagnostic port to any of the data lines on the PCM connector. One or more should have continuity. If none of them do, it is a mission to find the break.

With everything connected, I would also validate the 12v power connector and the ground connections on the diagnostic port function. Below are the pin outs for the data connector.
https://cimg0.ibsrv.net/gimg/monteca...523fecc351.jpg

The diagram below explains how to build an "Off board harness" (used to power and program a PCM without it being in the car). Ignore how it shows connecting the PCM for a DLC, focus on the pins on the PCM and what they are labeled as. By no means is this all the power/ground/data pins, but this was a quick find for me. I know these pins are used (as I built one of these harnesses and I have used it a few times). Validate the grounds and 12v are good on this connector. Also, going back to the continuity testing, this gives you some definite data pins to check out between the PCM and diag port (as I said, no guarantee these pins connect without further checking of the shop manual, BUT, I would guess at least one connects between this PCM connector and the diag port).
https://cimg3.ibsrv.net/gimg/monteca...38c64eebaf.jpg

I hope I did not confuse things......

plumbob 10-11-2017 08:38 AM

Thanks for visuals Jason, a picture is worth a thousand words:thumbsup:

N_robertson 10-16-2017 01:58 AM

Huge Update!!

Ended up borrowing my buddy's tech 2 scanner... Plugged it in and it said it couldn't connect with the PCM... thought this was weird and popped the hood to check if there was potentially a break in the harness somewhere that I'd overlooked... Turns out when the rabbit chewed through my MAF wires, it also chewed up my harness for the PCM... A few butt connectors later, the car runs and drives without any issues. I want to thank everyone who has posted on this thread in an attempt to help me!

plumbob 10-16-2017 10:13 AM

Congratulations, what a relief eh?

Blasted wabbits...lol

wht02monte 10-16-2017 11:30 AM


Originally Posted by N_robertson (Post 706940)
Huge Update!!

Ended up borrowing my buddy's tech 2 scanner... Plugged it in and it said it couldn't connect with the PCM... thought this was weird and popped the hood to check if there was potentially a break in the harness somewhere that I'd overlooked... Turns out when the rabbit chewed through my MAF wires, it also chewed up my harness for the PCM... A few butt connectors later, the car runs and drives without any issues. I want to thank everyone who has posted on this thread in an attempt to help me!

LOL How in the world..?:rotfl:


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