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Switch OFF, wipers ON...

1553 Views 6 Replies 3 Participants Last post by  Candyllac
I'm working on an '08 CTS. The wipers and window washer come on intermittently even though the switch is off. Testing I found a square wave signal on the wire from the washer push button switch to the body control module. All of the other parts of the circuit (low, intermittent, high) are pull-down circuits and therefore have the typical system voltage at rest. When a switch is activated, the voltage is pulled to ground.
Has anybody ever seen this square wave?
BTW, all normal functions work (mist, low, intermittent, high)... when it's not acting up.
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There, problem solved. On a whim, I cleared the BCM codes (U1511 & B1433) this morning and the square wave went away, to be replaced by a straight 14.5V DC voltage signal.
The BCM supplies system voltage to the different contacts of the wiper/washer switch, the switch in turn pulls the signal to ground upon activation. The BCM monitors each of these outputs to determine whether all is well.
My guess is there is a software glitch in the BCM causing this square wave. Clearing the codes somehow corrected the glitch. But I believe the problem would have come back sooner rather than later...
I put a BCM in the car, then had a guy come out to the shop and flash it.
Hi all,
So, this car came back yesterday with the wipers coming on randomly again. First thing I checked was for the square wave on the pink wire (push to wash button). The signal was a steady 12V signal, and every time I activate the push button the signal is pulled to ground, exactly as designed. Though I can't get it to act up, I did see the wipers come on as the customer pulled into my shop yesterday.
Again, this is both the wiper and washer coming on unrequested.
Checked codes and found U1511 & B1433.
B1433: ignition switched power relay 2 circuit.
In both Mitchell & Alldata, I'm unable to find any relay 2, and the only relay I can find that is controlled by the BCM is the main ign relay in the underhood fuse box. Problem is, this relay controls power to both the PCM & TCM, and there are no powertrain codes and the owner says the car hasn't skipped a beat since they bought it new...
As far as the U1511 code goes, I am unable to find any reference to it on either Mitchell or Alldata. I was able to get the local GM dealer to fax me a few page troubleshooting article on this and a couple other U codes, but according to the article the code relates to issues with the power windows and the compass?? So I questioned the customer again and they say the windows have never glitched, and they had no idea there was a compass in the car... Interestingly, on my test drive today one of the first things I noticed was the "N" on the instrument cluster, right dead center of the dash - which changed to "E" when I turned...
The only thing out of the ordinary I noticed during my test drive today was, I glanced over to see the pop-up screen for the sound/nav system was blank, as in no display. Almost immediately it came on.
So I'm looking for some direction. The wiper switch appears to do everything it's supposed to do with no glitches, etc., as seen on the scope.
I'm pretty confident, based on the schematics, that the problem is either in the BCM or the switch. I don't see how it could be the motor or the washer pump.
The only thing I can think to do is to disconnect the switch and give the car back to the customer for a trial of sorts.
Any other ideas?
Thanks in advance,
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Thanks for the compliment, both on the name and the knowledge.

In regards to the problem at hand, I found that GM recalled a series of car models, this car included, to remove the heated window washer nozzle feature. I read the recall: it says to cut the two wire harnesses that feed the heater unit, staggering the cuts to the wires so that when they are taped together they can't accidently touch. The wires were to be cut between the heater unit and the nearby connectors. My guess is that GM wanted the connectors to remain sealed so as to prevent anything getting into the ends of the connectors. Well, the tech who handled the recall on this car didn't follow the procedure. Instead (s)he just unplugged the connectors and taped them up.
Interestingly, of the seven wires involved, two of them, when shorted together, will activate both the wipers and washers. Not only do the two wires share the same connector, they are in adjacent cavities... And the end of the connector and the wire terminals themselves were corroded.
While it's possible - maybe even likely - that this is the smoking gun, I said the same thing about the BCM during the last go-round. So this time I'm cautiously optimistic. The customer will pick the car up in the morning and hopefully won't be back for the same problem next month...
Wish me luck.
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What year is your Burb?
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