08-06-03-006B Engine Running with Key Off Continuous Run - Sensing and Diagnostic Module (SDM) No Communication Service Air Bag Light Illuminated DTCs B1440 P0381 or P0650 (Install Diode to Solenoid Relay) - (Aug 2 2012) Relays
|Subject:||Engine Running with Key Off, Continuous Run – Sensing Diagnostic Module (SDM), NoCommunication, Service Air Bag Light Illuminated, DTCs B1440, P0381 or P0650 (InstallDiode to Solenoid/Relay)|
|Models:||2007-2013 Chevrolet Silverado 2500-3500 Series|
|2007-2013 GMC Sierra 2500-3500 Series|
This bulletin is being revised to add model years. Please discard Corporate BulletinNumber 08-06-03-006A (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 Messageare illuminated.Cause
These vehicles may be equipped with aftermarket equipment, i.e. a snow plow or a saltspreader system, that is controlled by a large solenoid or relay. When an electromechanicalsolenoid or relay is de-energized rapidly by a mechanical switch or semiconductor,the collapsing magnetic field produces a substantial transient voltage in its effortto disperse the stored energy and oppose the sudden change in current flow. Thesevoltage spikescan 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 controlaftermarket equipment, the spikes can be transmitted onto the circuit. The spikescan 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 topass retained accessory power onto the Run/Crank circuit keeping the engine controlmodule (ECM) on until retained accessory power goes low.
If the sensing diagnostic module (SDM) is damaged, the SDM will not communicate, andit will illuminate the supplemental inflatable restraint (SIR) lamp and the ServiceAir Bag message.Correction
Important:DO NOT replace the TCM or the SDM until the root cause of the condition has been identifiedto 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 voltagespikes from being transmitted onto the Run/Crank circuit.
Install a diode, P/N?12112422, across the coil of the solenoid. It is important thatthe striped end of the diode be connected to the positive terminal of the coil andthe other end of the diode be connected to ground.
Important:Be sure to insulate the diode with heat shrink tubing before installing as shown inthe picture above.
Notice:Some solenoids/relays may only have a positive post and will get their ground throughtheir mounting bracket. In this case, the striped end of the diode is to be connectedto the positive terminal and other end should be connected to the ground of the solenoid/relay.
fuse hot at all times switched ignition diode aftermarket relay/solenoid ground to on equipment
Install a diode, P/N?12112422, across the coil of the relay. It is important thatthe striped end of the diode be connected to the positive terminal of the coil andthe other end of the diode be connected to ground.