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Old 08-06-2011, 05:23 AM   #23
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greenman is a jewel in the roughgreenman is a jewel in the roughgreenman is a jewel in the rough
Join Date: Mar 2010
Posts: 1,923

2009 AURA XE
Default Re: 2007 Aura Instrument Cluster Problems

Originally Posted by kcarter2515 View Post
So it looks as if I have to take this into a dealership that has a Tech 2, which will most-likely be my local Chevy dealership.

One thing that I just don't understand is why the odometer reading on the new cluster won't budge! It just stays put at 52,946. Must be some sort of security feature. I mean, it's so easy to rip a cluster out and throw in a new one, I guess GM had to safeguard themselves somehow...

Thanks again for your help, everyone. I'll keep you posted when I get this sorted out. I'm letting my sister drive the car to Toronto for the week, so it might not be until the following week.
I found the answer to that question. The IPCs are VIN-locked. I am sorry I did not know that before you made your purchase. I am hoping the Tech 2 can open the VIN lock, but I honestly don't know if it can.
There is a redundant system that maintains the odometer in both the BCM & the IPC on this model. The BCM keeps the count but the IPC remembers the last count received. Unfortunately, GM does not maintain a standard method across models. Some models maintain the odometer in just the BCM, others in just the IPC. Nothing is simple anymore with computer control. Nothing can be assumed. Maybe it's not even consistent between Aura model years (which would make the cheese even more binding).

#PIC4554A: Swapping Clusters / Mileage Will Not Accumulate - keywords BCM counter inop inoperative IP IPC increase instrument locked MEC miles odo odometer swap trip - (Nov 12, 2008)

Subject: Swapping Clusters/Mileage will NOT Accumulate

Models: 2007 Saturn Aura


This PI was superseded to update model years. Please discard PIC4554.


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

In the cluster there is a component called a MEC (Manufacturing Enable Counter) that counts down from 256 to 0 and reduces 1 count per ignition cycle. When the counter gets to 0 the cluster is "Locked" and therefore whatever VIN is in the cluster at that time remains and it is locked. When you put a locked cluster into another vehicle the trip mileage will accumulate and roll over at 999.9 but the mileage on the permanent odometer will not increase. The mileage however, is stored in the BCM and when the correct cluster is put back into the vehicle the mileage should read correctly.

Note: Production (Fairfax) made a recent change to set this MEC to 0 when it passes DVT. Therefore when a car gets to the dealership and you swap a cluster (for testing purposes) it will not work correctly.

While it is not recommended, a cluster may be swapped from another vehicle. You need to drive the vehicle over 1 mile to verify that the regular odometer will increase. If it increases then cluster will work in vehicle. If however, the mileage doesn't increase (remember that trip odometer will increase) then cluster is been locked (MEC = 0) and will not work in the vehicle.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Last edited by greenman; 08-06-2011 at 05:31 AM.
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