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Discussion Starter · #1 ·
I think (pretty sure) my computer is dead. I've checked battery, grounds, fuses, fuse panels, etc.

Car will not start. If we jump the solenoid it turns over but it's not getting any gas. The ecu talks to the pcu to tell the fuel pump to start... This process is not happening. When hooked up to an obd II reader I get no communication whatsoever. I have a 2010 and would need a unit from a 2008 up. Gm lists none available in Canada not sure about the US but I assume the parts manager at the dealer checked.

Unless someone knows a direct part replacement from another vehicle with another part number in kinda screwed...

Any ideas??
 

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There is no PCU in the Kappa platform.


There is an ECM (Engine Control Module) and if you have an automatic transmission there is a TCM (Transmission Control Module). The TCMs only involvement in the starting sequence is if the car is in park/neutral. Other then that it really does nothing during the starting. Now the BCM (Body Control Module) is what handles telling the ECM to start the car. There is a TDM (Theft Deterrent Module) attached to the steering column under the key cylinder. This module is what reads the transponder code from the key and validates that it is a good code. When that happens a special password gets sent from the TDM to the BCM letting the BCM know that the key is a valid key. Once the BCM knows the key valid then it will instruct the ECM to start the car of the key has been turned to the start position. How it instructs the BCM to start is done over 2 wires. one wire is an ignition wire and the other is an accessory wire. When the ECM sees voltage on only the ignition wire the ECM starts the car. When the voltage on both the accessory and the ignition wire are present the ECM known to disengage the starter.

There are other things involved as well like clutch switches if you have a standard transmission. But that is the quick and dirty of how it works.

If you turn your key on and the gauges go all the way up and all the way back down you probably don't have a communications problem and you need to do some more checking as to where the problem could be. My questions start off here..

What does the light on the dash that looks like a lock do when you try and start the car? Is it blinking or lit solid?
Does the car crank?
Does the car start up and then stall?
Turn your low beams on and leave them on while trying to start the car. What do the headlights do when you do this, do they dim, turn off completely or no change at all?
 

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Discussion Starter · #4 ·
I get 0 Guage movement. From rpm gas and speedo

Zero crank no power to the selenoid, and no fuel pump. I also get no climate control.
Only the radio, door locks and windows work.
 

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what year and trim level is your car?
 

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Is it automatic or standard?
 

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OK so you have HS CAN in the vehicle...

This is the route the CAN wires takes..

On the passenger side of the car under the carpet against the firewall is the BCM (Body Control Module) This body control module is a gateway or a bridge between data networks in the car. One of the data networks is called HSCAN (High Speed Controller Area Network) and SWCAN (Single Wire Controller Area Network). The SWCAN connects systems in the car that are not essential to the operation of the vehicle, things like the radio, audio amplifier, OnStar, DIC (Driver Information Display) and the IPC (Instrument Panel Cluster). The HSCAN connects the ECM, PCM and EBCM (Electronic Brake Control Module). Both networks are connected to the BCM. The ECM outputs all kinds of vehicle metrics onto the HSCAN network the BCM receives the data and then transmits some of it onto the SWCAN network. The IPC uses the information and displays it to the driver.


The gauges going all the way up and then back down again is not a function of the IPC. It is a function of the ECM. so if the gauges do not move then there is an issue with the data getting from the ECM to the BCM and then to the gauges.

Because of how the HSCAN network functions if there is a break somewhere in the wire the entire network stops functioning. Where as with the SWCAN If the wire gets broken it will stop some of the devices from communicating not all of them.


The HSCAN network wires run from the diagnostic connector under the steering column over to the passenger foot well to the BCM. From the BCM they go through the firewall and come out by the battery under the air exchanger for the HVAC. from there they travel to the front of the car just above the frame. They pass next to the hood hinge to the front bumper. They cross to the drivers side just behind the bumper cover. once they get to the hood hinge on the drivers side they head towards the firewall. Once they get to the shock tower the harness drops low and connects to the EBCM.The EBCM liiks like a metal block with 4 tubes coming out of it. Then the wires come back out of the EBCM and head to the drivers side fender. This is where the ECM and the TCM are located. The wires goes into the PCM and then come out of it and go into the ECM.

If either the EBCM or the TCM is not plugged in properly this will cause the network to not work. Over by the battery just below the under hood fuse box there is a rats nest of wiring. There are 2 inline clips that are attached to the bracket that holds the fuse box. Unplug those clips and plug them back in. Do it a few times. The pins could have gotten some corrosion on them. Inspect the entire length of the wiring harness from the firewall to the ECM. make sure there is nothing cut, also make sure the harness has not rubbed anything and worn a hole through it. Inspect the diagnostic connector and make sure it is not damaged.

It doesn't cost a penny to do those things and is advisable to do before buying anything.

Report back any findings.
 

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I don't know the exact programming of the modules.

I just went through this exact same issue not a couple of months ago with @rob the elder 's car. That is why I know what to ask and look for if there is a communications problem. @rob the elder did exactly the same thing as the OP is looking to do, he bought a new ECM and it didn't work. I went and took a look at the car with him and we found an issue with the HSCAN wiring. We fixed up the wiring and made it as close to new as we could without replacing the actual wires (might replace them at some point) and the car started right up.
 

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Discussion Starter · #12 ·
There was tons of corrosion from water in the fuse box in the passenger well. We removed everything cleaned the corrosion. My gauges are back and so is my hvac.

I still have no communication to the ecm or power to the igniter wire to the solenoid.

All other wires traced around the car seem ok.

This is really boggling my mind. When we try to force start the solenoid the car cranks but will not start.

No more lights come on, even the check engine light doesn't. The security light come on for a sec but goes out right away. I tried resetting the pass code 3 also to no avail.
 

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Discussion Starter · #13 ·
Ok the check engine light is back on and flashing madly when in the on position.

Could it be a ground?
 

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If you have a corrosion problem at the underwood fuse box I strongly suggest you look at the 2 inline clips under it. And make sure they are cleaned up as well.

On the HSCAN network there are 2 wires one is can high and the other is can low. Effectively receive and transmit. The gauges can be working because the BCM is getting data from the EMC but the BCM is not able to tell the ECM to start the car. So 1/2 of the data system is working.

The CAN high and CAN low wires are brown and brown/black I believe. I know one of them is brown the other could be brown/black or brown/white I can't remember off the top of my head. The wires will be twisted together.

If you have a corrosion problem at the fuse box check the connector that plugs into the EBCM, TCM and the ECM and make sure the pins in the module are clean as well as the sockets in the clips.
 
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