My neighbors LMM acquired a strange quirk...it won't shut off when you turn the key. Once the key is out of the ignition, he can step on the brake and it quits.

Dealer replaced the computer and that fixed the problem for a week or so. Now it is doing the same thing.

Any ideas what the problem is?

sounds like it won't shut off untill you press on the brake.:D

Sorry, I can't help ya!

Didn't this come up in another thread not too long ago ??

Never heard what the problem was though, maybe a bad ignition switch ?

sounds like it won't shut off untill you press on the brake.:D

Sorry, I can't help ya!


:funnypost

here,s the other thread but they never said what the problem was.

http://www.dieselplace.com/forum/showthread.php?t=281965

.

here,s the other thread but they never said what the problem was.

http://www.dieselplace.com/forum/showthread.php?t=281965

.


Thanks!

Has there been anything wired to the fuse panel behind the parking brake? There is a keyed hot in there that if you run anything to it the engine will stay running even after key is pulled until you open the door. Its weird as hell, but it happened to me :o:

Does it have remote start?

Does it have remote start?

That was going to be my question!

Has there been anything wired to the fuse panel behind the parking brake? There is a keyed hot in there that if you run anything to it the engine will stay running even after key is pulled until you open the door. Its weird as hell, but it happened to me :o:

It's called the RAP circuit, (Retained Accessory Power).

Relay Control of Retained Accessory Power (RAP)
The BCM keeps the Retained Accessory Power (RAP) relay energized during all power modes, except Off-Awake and Crank. The relay is also
energized for approximately 10 minutes after shutting the ignition OFF and removing the key, providing no door is opened. The BCM will deenergize
the RAP relay at the same time as the serial data message is sent to end RAP.
The devices powered by the accessory relay during the RAP power mode are the sunroof, power window switches and Brake Transmission
Shift Interlock (BTSI)/Park Lock.

Above info found at GM Upfitter, page A-9:
http://www.gmupfitter.com/publicat/2008_BB/08REV_LDCKFST_Elec_D3.pdf

My friend that this happened to just got it fixed. It was the tranny computer. Don't ask me why, doesn't make any sense to me.

Dealer just this weekend was able to fix the truck (after several previous attempts including a ECM) They finally replaced the BCM which seems to have been the culprit. It's all "foreign" to me but the dealer commented to my neighbor there have been 6 updates to the BCM...this is new to me!! Anyone heard of BCM updates (I assume reflash?)

It's called the RAP circuit, (Retained Accessory Power).

Relay Control of Retained Accessory Power (RAP)
The BCM keeps the Retained Accessory Power (RAP) relay energized during all power modes, except Off-Awake and Crank. The relay is also
energized for approximately 10 minutes after shutting the ignition OFF and removing the key, providing no door is opened. The BCM will deenergize
the RAP relay at the same time as the serial data message is sent to end RAP.
The devices powered by the accessory relay during the RAP power mode are the sunroof, power window switches and Brake Transmission
Shift Interlock (BTSI)/Park Lock.

Above info found at GM Upfitter, page A-9:
http://www.gmupfitter.com/publicat/2008_BB/08REV_LDCKFST_Elec_D3.pdf



no.... The "RAP Circuit" is not really a circuit. Everything in the truck is turned on and off with a data signal, not an ignition-hot power wire. Its not like there is a wire that is "+12volts" when "RAP" is active.

normally "RAP" is controlled by the BCM, so it doesn't surprise me this was the culprit. the very first thing the dealership should've done was check for software updates. while i look for any aftermarket stuff improperly added, i'll have the tech2 running, looking for software updates. about half the time, thats it.

I might have found an answer for the continuous running following shut off. Its a service bulletin that I located...

Tried to attach the pdf file but for some reason it wont attach to my reply?????????

Ok, I scanned it into a word doc. Lets see if this will attach....

what is the tsb number

Everything I try to post a copy of it wont work for me....
Here is the Service Bulletin info: 08-06-03-006 Dated June, 2008

#08-06-03-006A: Engine Running with Key Off, Continuous Run - Sensing and Diagnostic Module (SDM), No Communication, Service Air Bag Light Illuminated (Install Diode to Solenoid/Relay) - (Jan 29, 2009)


Subject: Engine Running with Key Off, Continuous Run -- Sensing Diagnostic Module (SDM), No Communication, Service Air Bag Light Illuminated (Install Diode to Solenoid/Relay)


Models: 2007-2009 Chevrolet Silverado 2500-3500 Series

2007-2009 GMC Sierra 2500-3500 Series




--------------------------------------------------------------------------------

This bulletin is being revised to update information and add a procedure. Please discard Corporate Bulletin Number 08-06-03-006 (Section 06 -- Engine/Propulsion System).


--------------------------------------------------------------------------------

Condition
Some customers may comment on the engine running for 10-15 seconds with the key off, and/or the supplemental inflatable restraint (SIR) MIL Lamp and Service Air Bag Message are illuminated.

Cause
These vehicles may be equipped with aftermarket equipment, i.e. a snow plow or a salt spreader system, that is controlled by a large solenoid or relay. When an electromechanical solenoid or relay is de-energized rapidly by a mechanical switch or semiconductor, the collapsing magnetic field produces a substantial transient voltage in its effort to disperse the stored energy and oppose the sudden change in current flow. These voltage spikes can occur at the positive terminal when the solenoid or relay is de-energized (keyed-off). If a solenoid or relay is wired onto the Run/Crank circuit of the vehicle to control aftermarket equipment, the spikes can be transmitted onto the circuit. The spikes can permanently damage the internal circuitry of the TCM and/or the SDM.

If the transmission control module (TCM) is damaged, it is possible for the TCM to pass retained accessory power onto the Run/Crank circuit keeping the engine control module (ECM) on until retained accessory power goes low.

If the sensing diagnostic module (SDM) is damaged, the SDM will not communicate, and it will illuminate the supplemental inflatable restraint (SIR) lamp and the Service Air Bag message.

Correction
Important: DO NOT replace the TCM or the SDM until the root cause of the condition has been identified to the solenoid/relay voltage spikes.

To prevent damage to any of the sensitive electronic components on the bussed circuit, the solenoid/relay MUST have the control circuit suppressed with a diode. The diode will prevent the voltage spikes from being transmitted onto the Run/Crank circuit.





Install a diode, P/N 12112422, across the coil of the solenoid. It is important that the striped end of the diode be connected to the positive terminal of the coil and the other end of the diode be connected to ground.





Important: Be sure to insulate the diode with heat shrink tubing before installing as shown in the picture above.

Notice: Some solenoids/relays may only have a positive post and will get their ground through their mounting bracket. In this case, the striped end of the diode is to be connected to the positive terminal and other end should be connected to the ground of the solenoid/relay.





Install a diode, P/N 12112422, across the coil of the relay. It is important that the striped end of the diode be connected to the positive terminal of the coil and the other end of the diode be connected to ground. Be sure to insulate the diode with heat shrink tubing before installing.

Parts Information
Part Number
Description
Qty

12112422
Diode
1


Warranty Information
This repair will not be covered under warranty due to the failure being caused by an aftermarket accessory.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

How is that for ya

So in the other thread that had a similar problem, they replaced the TCM and it worked, maybe it was damaged internally like the TSB says because of a addon accessory.

.

Well I think I finally got the original document (pdf) of the Service Bulletin for the issues with the engine staying on when the key is turned off.

You got to love this site.
It amazes me how quickly you guys can figure out and respond to even the weirdest problems with these new computer controled trucks. Grandpa's thinking it's a bad ignition switch because the 12 volts to his fuel selenoid must come from the ignition switch right? Wrong! It's got a c o m p u t e r or better yet several c o m p u t e r s.

Good job guys.