Thanks for your input CCC. I don't know the voltage at the door switch. As you mentioned, high temp can cause Copper to darken. It also develops a natural dark patina with age. The other trace was bright and there was no sign of any form of corrosion on either one. The contacts from the push buttons were bright and clean. Whatever the cause, removing the oxide layer made the switch work as it should.The discoloration on the copper etches is caused by corrosion, --not overheating, which would be caused by high current, which doesn't exist in this circuit. Placing a conformal coating over the circuit board to reduce the etche's exposure to the elements is about the only way of making them as bullet-proof as possible. In this case, darkened copper is a normal condition.
CC
CCClark: Most times my 2008 XLR Passenger door will not open when the interior door panel button is pressed. The button illuminates and activates the interior lights but door does not unlatch. Have you heard of any problems with the Door post latch solenoid? Is it very difficult to access?Timely thread; I've been trying to help someone with a related problem.
The XLR's windows have two built-in functions that are controlled by their respective door modules: Normalization and Indexing. Normalization is the process of calibrating the window position when a door latch button is depressed. The upper-most window position is called the Zero Position. All calibration is derived from the Zero Position. The Zero Position is determined by one of two things - the Anti-Trap location (if something blocks the window from raising and an over-current condition is detected) or the window position switch is held for greater than half a second when it's raised to it's highest position. If the Anti-Trap feature is enabled, that location becomes the new Zero Position.
Indexing occurs when a door switch is activated. The window glass should drop about 4 mm until the door position switch is depressed, and will raise again after the door position switch indicates the door is not ajar/open. The whole point of Indexing is to effect a watertight and acoustic seal between the window and roof. There's a slight delay for the door latch to open as the sensors communicate via the Class 2 bus with the door module to determine where everything is. Occasionally, I have to prod the door switch pad a few times to get it to open, but the system works pretty well for what it is. This was a pretty cool feature when it first came out.
CC
I have had no problem with the interior door open switches. The only problem I had, with door openers, was the passenger one, to open the door from the outside, wouldn't work. I removed it (2) black phillips head screws,and took it to the kitchen table. Then I removed 6 very tiny phillips screws on the back, to open it. I cleaned the copper circuit board with "Prep Sol."Then I lightly sanded that circuit board, cleaned it again with "Prep Sol," and re-installed it. It works like as new one now!!
Correct. We're discussing a door latch issue when the interior switch is pressed.
If the door unlatches when the exterior switch pad is pressed, the latch is most likely fine, which tends to direct the troubleshooting in the direction of the interior switch. But there's more to it; after all, this was Cadillac's first attempt at a seriously interconnected vehicle, so we have to look at the Big Picture and try to avoid tunnel vision when troubleshooting.
Three modules (and the interior door switch) have to operate correctly in order for the passenger side door latch to do it's thing. The RCDLR, (Remote Control Door Lock Receiver) the PDM, (Passenger Door Module) and the BCM (Body Control Module) make the magic happen. The RCDLR and BCM signal the PDM to unlatch the door.
Digging a little deeper, the RCDLR receives the UNLATCH signal from the exterior and interior door switches. First, it checks the status of the door to determine if it's locked or not. If the door is unlocked, the RCDLR applies a ground to the door latch solenoid. But wait, there's more! You need a supply voltage applied to the solenoid to complete the circuit.
The PDM receives the door switch UNLATCH signal at the same time as the RCDLR. It checks the status of the window to figure out the height of the window. (This is where the window index count memory resides for each door that the folding top control module checks before it will move the top.) If the window is below it's index position, the PDM allows the latch to be opened. If the window is above it's index point, it drops the window slightly prior to the door unlatching, to avoid damaging the seal and or window glass. When the window is in the correct index position, the PDM sends a signal to the BCM to apply voltage to the window latch. (This is another clue. . . can you tell where this is going?) Remember, all of the above assumes the windows are indexed properly. If the top isn't working, that's always the first thing to check, by the way.
To summarize, the BCM supplies the solenoid voltage and the RCDLR supplies the ground path to complete the circuit, throwing the latch.
Here's what I recommend now that you have a good idea of how the circuit should operate:
1. With the passenger side window fully raised, press the passenger side interior door switch. Does it: Index (drop 4 mm?) If so, does the door latch solenoid make any noise?
2. With the passenger side window fully lowered, press the passenger side interior door switch. Does the door latch operate or make any noise? (It's okay, press your ear against the exterior door panel while you press the switch, nobody's watching. . . right?)
3. Repeat steps 1 & 2 with the exterior switch, which should work fine, but inquiring minds wanna know, just to be sure.
In theory, if the exterior switch operates under these conditions, then the interior switch should too, since they use almost identical signal paths, with the exception of a few wires, connectors, and of course, the two unlatch switches. But seeing as how I'm here and you're there, remote troubleshooting always boils down to educated guessing based on good symptom elaboration, so the more info you can give me, the easier it is to offer potential solutions.
Drink a beer or two to celebrate your new passenger side door latch troubleshooting skills, then report back with the answers to questions #1 and #2, and I'll walk you through the next exciting steps. One warning: You'll need to buy more beer!
CC
