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2006 XLR. Past: 1961 Convertible, 1977 Coupe DeVille, 1979 Eldorado, 2006 CTS
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Discussion Starter #1
I’m starting this thread because, of course, I have a trunk/top problem with my 2006 XLR, but also because I want to throw out an appreciation to C C Clark. CC, on everyone’s behalf, I want to thank you for the buckets of great advice you have given everyone over the years; you must have collectively saved us Cadillac owners hundreds of thousands of dollars by now. You da best!

OK, so last year I noticed the trunk would rise more slowly in hot weather; had a dealer check it out (yes, certified XLR mechanic), even offered to pay for a PM, lubrication, or whatever they might do to revitalize the top/trunk system. He said there was nothing wrong and he didn’t have any precautionary procedure he could do to it.

Well, I don’t have to tell you that now the trunk won’t open at all if the car has been sitting in the sun (unlatches but won’t rise), so I brought it to a different dealer (with another “certified” XLR mechanic). He said the gas struts were shot - $340 to repair; I thought wow – that’s actually great news because I can probably do that myself for a lot less.

But in searching the forums I began to have doubts. According to the forums, it sounds like the most common symptom of shot gas struts is that the trunk does not stay up or slowly lowers itself after opening. Mine does not have that problem, in fact once my trunk is open it almost feels like it’s locked in that position. However on the other hand, unlike hood struts which only help support the hood when it is most of the way up (due to the angle) the geometry of the trunk struts is such that they are pushing the linkage straight up even when the trunk first opens, so maybe they do do a lot of the work right when it opens?

I’m thinking gas struts don’t last forever and I should maybe just replace them anyway, but I’d love to have your input on whether you think this is my problem, CC. Thanks!
 

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'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
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First, thank-you Dave for the kind words.

Just so we're on the same page terminology-wise, the rear deck lid's primary lifting mechanism are a pair of hydraulic cylinders; they are assisted by a pair small gas struts partially hidden by the rat fur on the side of the trunk. The reported failure rates for the gas struts are low, but like anything else, they aren't immune to failure. Make sure your Folding Top hydraulic fluid level in the reservoir on top of the pump is between the min/max marks.

There are a few other things you can do before you start buying parts. The first question I have is in relation to the symptoms you describe. You said the top is failing when it's hot. Does it operate nominally when it's cool? There is a thermistor located on the inside/bottom of the Folding Top hydraulic motor that will inhibit motor operation if it's too hot or cold. It should flag a message on your DIC to report this.

With a couple of beers and a trusted helper, have them press the Folding Top Control switch while you gently pull upwards on the rear deck lid. If a strut, (or a hydraulic cylinder) have failed, this should enable the pump to raise the deck lid, and you can verify the pump's operation. If the Rear Deck lid raises, but settles back down when you let go of it, either hydraulic fluid is leaking by a cylinder seal, or the gas strut(s) aren't doing their job.

If the Rear Deck lid unlatches, but nothing happens, your pump may have failed. Usually, (and it certainly happened to me) if the pump is failing, it will partially move the top but stop at some point when it can't supply enough pressure. It's an expensive repair, and a worst-case scenario, to be sure. Listen for it to try to operate; at least you know it's getting a command to run. Another item that can fail and cause the Rear Deck lid to not move is a Solenoid valve in the hydraulic manifold which supplies hydraulic oil to the lift cylinders. These can be individually operated and verified with a Tech 2.

If the gas strut(s) have indeed failed, this would be the cheapest repair and something you could replace. Gather some more symptoms, and if you need to replace them, I can write up a procedure. I'll hit the books later and see if there's a documented checkout for them. Since they can be removed easily enough, you could support the Rear Deck lid with a 2x4, pull them off and compare each by compressing them.

CC
 

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2006 XLR. Past: 1961 Convertible, 1977 Coupe DeVille, 1979 Eldorado, 2006 CTS
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Discussion Starter #3
Thanks for comin' right back, CC (as usual). Trunk and top all work perfectly when cool. When hot outside trunk will rise but slowly. When hotter yet or sat in sun for a while, trunk unlatches but can't rise (but never falls once open). Hydraulic fluid level is normal. I'll try your test to raise it by hand next time I take it out (no shortage of hot weather here now), but does this narrow it down any?
 

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'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
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Yes Dave, it does; good job on the feedback.

The fact that the latch is releasing is a good thing. Does the pump make any noise when it's supposed to run? If you're able to assist the Rear Deck lid, (and the pump is indeed running) that points to a sensor or lift mechanism issue. If the pump doesn't operate, that points more to the pump or control circuitry in the FTC module.

You may have a faulty thermistor disabling the hydraulic motor (thermistors alert the FTC module to stop the flow of current to the motor, when the temperature is outside of a set operating range.) They won't always give a DTC to a Tech 2 - especially if the pump is tested when it's cool. If you have access to a Tech 2, it's easy to check the condition of the thermistor by inspecting the "Pump Motor Temp Sensor" value (which reads directly from the thermistor in F/C) and the status of the thermistor itself in the "Pump Over Temperature Sensor" value, which reads as Over Temp or Normal. Obviously, an Over Temp status would be a failure condition. If the thermistor voltage drop indicates it's too cold, the "Too Cold For Top Operation" status will read: YES when the Folding Top Control switch is released.

It kind of sucks not having a Tech 2 and being reliant on a Tech at a dealership, but it is what it is. The XLR is not a very good car for the DIY type, unless a Tech 2 is readily available. But it is one heck of a tool to peer inside the innards of the XLR if you're a curious geek, like me.

I've attached a few pics to show what's where. The thermistor is located under the black, plastic cover of the motor/pump.

CC
 

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87 Allante, 06 XLR
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My wife's '06 XLR has same problem except when you try to activate the top the DIC says Pump motor is over heated. Took it to local dealer in Ft Walton Beach FL who I doubt has an XLR trained tech and they claimed the pump motor was burned out. They want $1800 to fix it! I have been able to muscle the trunk open using the rear bumber key but that is not an option for my wife. My questions are is the pump and motor a single unit or can the motor itself be replaced/repaired? I have also looked for used items with no luck. Seems like due to the location any wrecked XLR would be a good donator. Is the transitor sensor replaceable? I have just joined the forum and found a wealth of info already.

Tim
 

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87 Allante, 06 XLR
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Another question is if I'm able to find a used pump/motor, are they universal over all the years the XLR was produced??

Tim
 

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'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
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Great questions Tim!

The part number for the hydraulic pump (which includes the manifold and solenoid valves is 88958028. It's applicable to all years (2004-2009.)

The pump is the motor, so the terms are interchangeable. As it spins, it moves hydraulic fluid to the lift cylinder path directed by one of the (five) open solenoid valves located on the hydraulic manifold. Opening the hydraulic bypass valve on the side of the manifold connects the supply and return side of the system allowing you to manually move the roof components easily (aka: cardio-pulmonary power.)

The pump has increased in price (from when I replaced one in 2008) to $1,015.11 (online @ gmpartsdirect) but that's to be expected as the vehicles age. If you end up having to replace the pump, the most painless way is to buy the parts and have a trained tech install them, since a Tech 2 will be needed to check it out when it's ready for operation. A chat with the Service Manager is usually positive, though they'll only warranty the labor and not the parts you supply. You''ll also need to buy an O-ring kit, since all of the hydraulic lines on the manifold need to be disconnected.

As for replacement thermistors, if you look on the picture of the case, you'll note the housing is crimped shut, meaning GM would rather you buy the whole assembly, instead of replacing a single two-dollar part. If the thermistor is indeed bad, you could conceivably remove the original through the access hole, and solder a new one in once you spec out a replacement. If the pump is burned out, the motor may be overheating and the thermistor will open, interrupting the power supply to the pump. You really need to determine what the cause of the problem is before you go throwing money at it. You could measure the resistance of the pump windings and have them compared to a known good pump. I can open my connector and verify the resistance if you want to go that route.

Here's how the temp sensing works for the Folding Top:

The pump temp is always monitored by the Folding Top Control (FTC) module for a too high or low condition via the thermistor. There are two types of temperature settings in the over temp range: a pre-alarm condition and an alarm condition. For high temps it's 221F and 239F. What this means is that if the thermistor reads 221F, the FTC module knows there's trouble in paradise, but will allow the pump to operate for the current cycle. It won't operate again until the temp drops below 221F. If the temp gets to 239F, the FTC gives a "No way Jose" command to the pump and nothing happens. At that point, a "TOP MOTOR OVERTEMP" message will be displayed on the DIC.

The thermistor monitors cold conditions and will not let the Folding Top move if the temp gets below -4F. This is probably to save you from frostbite if you're too hammered to know any better. If you're still coherent enough to be able to read, the DIC will display "TOO COLD TO MOVE TOP". The rear deck lid spec is a little looser. It will still operate all the way to -22F, to allow you to get that next beer out of the trunk.

If this isn't technical enough and you're suffering from insomnia, please continue reading . . .

The FTC monitors the thermistor every 300ms, which is roughly the same amount of time it takes me to spot a single woman sitting alone in a crowded bar.

A five volt signal is applied to the thermistor. As the pump warms up, the thermistor resistance decreases, and the voltage drop increases. The FTC module converts the voltage drop into temperature values. As the voltage/temp increases the FTC module monitors the voltage until it reaches a set point programmed into the FTC module. A Tech 2 will see a DTC of B3670 when the temp hits 203F. This may be the DTC your tech observed if he was scanning the system to troubleshoot the Folding Top.

One of the troubleshooting steps to isolate the faulty component in this case is to disconnect the pump connector to the FTC and see if the problem remains. If so, the FTC module is suspect. That would be a much cheaper repair. You could order and replace the module yourself, and have someone with a Tech 2 calibrate the top to the new FTC module.

Until you get the problem resolved, you can avoid the cardio workout and open the hydraulic bypass valve on the manifold to cross-connect the system and the Rear Deck lid should be easier to open manually. Instructions for lifting the Folding Top manually are in your owner's manual.

CC
 

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87 Allante, 06 XLR
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Thanks a bunch CC. I can understand how much you are appreciated in this forum. Because I'm working w/o a repair manual can you describe the locations of the pump connector to the FTC and the bypass valve on the manifold. I'm still going to try and find a used one in good condition before I invest in a new GM part.

Tim
 

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Tim,

See the photos above. The T-handle of the valve is on the side of the manifold (and displayed in the owner's manual.) The connector is also shown above and goes to the FTC module adjacent to the pump. The Service manuals are available from helminc.com.

CC
 
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