Keep the change

Here we have a 2006 Nissan Maxima with 129,002 miles on it. The vehicle is driven to the shop with a complaint of no instrument gauges, ABS and TRAC lamps on, and the heater panel selection buttons are illuminated even with key off. This happened all of a sudden. The shop called me in to look at the vehicle and diagnose the issue. I begin by confirming customers issues and a visual.

 

Ok this is with the car running for approximately 10 minutes. Fuel gauge and temperature gauge are inoperative.

Here we have the other side. No tachometer operation and various lamps on for the ABS/TRAC system. This problem is happening right now. My favorite type of issue. Now I can roll up my sleeves and get to work. Nothing worse in my business than an intermittent issue. It eats up a lot of time and they never seem to act up when I am testing. I do plenty of intermittent issues and it takes intelligent testing and patience. Some days I am neither intelligent or patient. Back to our issue. My next step is to hook up the scantool and take a peak at what is happening.

Here, I am using the Nissan Consult 3. A 2006 Nissan Maxima is a Consult 2 vehicle but Consult 3 and Consult 3+ are backwards compatible for diagnostics and sometimes for programming. I do a full scan of all modules for DTC (Diagnostic Trouble Codes). This is first page.

Here is the second set after scrolling down. It seems very apparent that I have CAN (Controller Area Network) issues. The common thread is the U1000 code. The other comes from experience I do not see a Instrument Cluster reporting or as Nissan calls it a Meter. When I see U1000 codes in multiple modules it usually means a module that should be there is not reporting. My next step is to use a very slick feature of this factory tool.

This feature is the CAN DIAG SUPPORT MNTR. My relationship with the Nissan Consult 3 scantool is a love/hate relationship. Some days I would like to turn my laptop into a Frisbee when using this tool. Other days I can't say enough about it. This is the feature that keeps me using it. I can select a module on the right and then the tool will poll that module and the module will show on the left which modules it is recognizing and communicating with. In this case I am asking the ECM what modules it sees. I see something right away.

Look at the red arrow. Presently the Meter is Unknown. All the other modules are OK or in other words they are present. Lets check another module.

Here we are asking the BCM. Same thing Meter is Unknown. See the pattern. I hit the Result box in upper right corner.

Here you will get CAN H and CAN L voltages as well as system voltages at the DLC. I usually sneak a look at this but always back it up with my labscope. In this case I don't need my scope. I know where to go but lets get some theory and wiring background.

Here is a partial wiring diagram of the system. It is enough for some theory and demonstration. You can see the combination meter a.k.a Instrument Cluster a.k.a Meter gets data from a module called an Unified Meter and AC AMP. Nissan loves to integrate modules for multiple tasks. It is one of things that make them very challenging. Let's get some theory behind the wiring.

  
From the factory service information. Pretty much what we see on the wiring diagram. So this module controls air conditioning control and processes signals from the CAN lines to send to the Instrument Cluster/Meter. I think we found a prime suspect. Let's get back to the car.

I have been here before. I know where this Unified Meter and AC Amp resides. Here is a shot of the ac panel, every light on. One word of caution here. See the aftermarket radio lurking underneath. I have seen incorrect aftermarket radio installations cause these issues as well. The customer confirmed that this radio has been in here well prior to this issue. See that white module above the ac panel? That is our culprit.

Some more screws and out it comes. Like I said been here before. As I am removing the module I hear rattling from the module as I turn it over.

Finally free at last and I can shake it and it sounds like a baby rattle. A quick sniff of the module reveals the smell of burnt electronics. See that small slit on the right side of the module? It is the perfect size for a penny, a dime, or a nickel. I always challenge myself as to how much change I am going to find inside and usually have a bet with the shop owner. I bet 6 cents. Incidentally, new modules come with a piece of tape over that slit.

I lost 11 cents is the winner. This is a very common issue. This 11 cents just cost this customer much, much more. I have seen this cause no starts if it shorts the CAN line down.

So common that Nissan issued a TSB about this issue. I tell the shop owner my findings and guide him through the TSB. A few days later a new module is installed and the Maxima is back to operating normally.

Here is a shot from another Maxima showing the area how it is stock and not torn apart. Keep that change off that ledge.