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1997 Chevy Cheyenne K3500, cc, lb, dly, dzl, 2002 Chevy Avalanche Z71, 2003 Chevy Avalanche Z66
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Discussion Starter #1
Back when my son bought me my Avalanche in October, the ABS light, the Parking Brake light, and the Service Brake System message on the DIC were all on. The used car dealership finally took care of replacing the ABS module, which turned out the ABS light on the dash. But the Parking Brake light and the Service Brake System message are still present. I finally popped the hood the other day to do some other ignition and door panel work and looked under the brake fluid reservoir for the sensor. To my surprise, the fluid level sensor and the connector and wiring harness were missing from under the reservoir. I cannot immediately find the wiring harness for the sensor in the engine compartment. Would anyone here know where the wiring for the brake fluid level sensor goes back to so that I can check to make sure mine is still intact? Does anyone have a wiring diagram for the brake fluid level sensor showing where it connects to?
Thanks In Advance
csltrains96
 

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1997 Chevy Cheyenne K3500, cc, lb, dly, dzl, 2002 Chevy Avalanche Z71, 2003 Chevy Avalanche Z66
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Discussion Starter #2
Still looking into this problem. Apparently not all trucks with the reservoir that has a spot for a sensor had one installed in that location. Would anyone here know the different conditions that would set both the Parking Brake light and the Service Brake System message on the DIC? I'd like to get this truck to stop dinging at me incessantly when I turn the key on!
 

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Only things I can think of other than a level sensor issue would be the switch on the parking brake being messed up so it thinks the parking brake is on. The other would be maybe a bad brake switch on the combination valve below the brake master cylinder.

#7 is a brake sensor in lower valve assembly
#10 is the valve assembly it sits in

166130


From what I can find from GM is that they all utilize a level sensor for that year but it's a bit hard to say 100% without a VIN.
 

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I don't know if this will help because i'm reading from a 2002 silverado truck diagram but, the P brake and service brake lamps are controlled by the electronic brake controller module (under drivers side frame rail) and brake fluid level sensor and then to a ground on the back of the block, near the center of the manifold. The brake fluid level sensor on my silverado is located on the right of the master cylinder under the resevoir as viewed from the front of the truck and it passes the ground on to the EBCM for serial data input to the Instrument panel. I'm not sure you have a ECBM since your truck is a year newer than mine.
 

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1997 Chevy Cheyenne K3500, cc, lb, dly, dzl, 2002 Chevy Avalanche Z71, 2003 Chevy Avalanche Z66
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Discussion Starter #5
Crispyt and silverado002 - Cryispyt's diagram does look like my setup. There is a spot for the level sensor in the bottom half of the reservoir (item #1 in the diagram), but no sensor installed, and no wiring harness to be seen. That's why I was wondering if anyone knew where the wiring was supposed to come from so that I could check to see if I had any ripped apart wires. But the diagram doesn't show a level sensor, either.
Would a bad brake switch on the combination valve (item #7) have any effect on the brake lights and cruise control? Those still work on my truck. I'll have to get out my DVM and check for continuity across the parking brake switch.
Thank you.
HisZ66
 

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If you want to send me the last 8 digits of your VIN I can see if it's supposed to have a brake sensor in the reservoir. I work at a GM dealer in parts, so I can see if it is supposed to utilize that part. I don't believe that they would affect your cruise control or your rear brake lights though.
 

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1997 Chevy Cheyenne K3500, cc, lb, dly, dzl, 2002 Chevy Avalanche Z71, 2003 Chevy Avalanche Z66
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Discussion Starter #7
Crispyt - sent you a message. Thank you!
 

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Your welcome, ill check it out tomorrow for you (Monday).
 

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So I ran your VIN this morning, according to GM it should have a brake level sensor on the master cylinder.

Sensor part number is: 18012741
Brake master cylinder part number is: 19209239

I would try to dig around a bit to see if the plug got tucked behind something. Unless someone cut it or changed the harness it should be there somewhere.
 

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1997 Chevy Cheyenne K3500, cc, lb, dly, dzl, 2002 Chevy Avalanche Z71, 2003 Chevy Avalanche Z66
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Discussion Starter #11
Thank you, Crispyt! I'll have to dig around in the engine bay this coming weekend.
 

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Forgot to mention that if you find that it has been cut, but there is enough wire to solder a new pigtail on the GM part number for the pigtail/connector is 88987993
If in a worst case scenario you find that the harness isn't fixable the part number for that should be 15137221. However in GM land the main harness, (15137221) is discontinued. But it looks like there are a few people selling them on eBay or you might have some luck at a local junkyard. Although it's probably not an easy job to replace as some of it also runs down the frame rail.


Just as a small bit of info in case you were ever curious, your truck was built on Thursday May 8th, 2003.

It also looks like your truck was originally sold at Rydell Automotive Group in San Fernando, CA on 6/28/2003.




It's been a slow day at work.. hah
 

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1997 Chevy Cheyenne K3500, cc, lb, dly, dzl, 2002 Chevy Avalanche Z71, 2003 Chevy Avalanche Z66
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Discussion Starter #13
Crispyt - in case you get another slow day.... If I can't find the wires due to a different harness being installed, wires have been pulled from way back, etc... Can you find where the circuit comes to a connector or something where I can splice in a set of wires? Something fairly accessible, maybe? Thank you for all the information!
 

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1997 Chevy Cheyenne K3500, cc, lb, dly, dzl, 2002 Chevy Avalanche Z71, 2003 Chevy Avalanche Z66
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Discussion Starter #14
I'm no stranger to making wiring connections. I have a soldering iron and heat shrink, butt connectors, T-taps, suitcase connectors, etc... I just need to know where I can establish the connection from. Thanks.
 

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I did a little digging around this morning, it looks like it should be a purple wire and a black wire for that sensor. Purple wire being the signal wire and the black wire being the ground for it. I'll keep looking to see if I can find a diagram of the harness. Unfortunately I don't get all the info working on parts here but I'll see what else I can find.
 

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166229


This probably isn't too helpful but this is the harness that the plug would be part of. It would normally be coming out near the number 11 designation in the picture.
 

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Don't know if this will help much but on my 2002 the purple wire goes from the brake fluid level switch to Connector C2 terminal B8 of the Electronic Brake Control Module. The black wire goes to the underhood fuse block on connector C3 terminal F6 then thru the fuse box to connector C3 on terminal F7 to a splice point S102 and then to G104 ground which is located behind the intake manifold on the transmission top bolt.

The ECBM is located under the drivers side of the truck mounted to the frame rail near the drivers seat.
 

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1997 Chevy Cheyenne K3500, cc, lb, dly, dzl, 2002 Chevy Avalanche Z71, 2003 Chevy Avalanche Z66
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Discussion Starter #18
Crispyt and silverado002 - Thank you so much for your time and information digging! This gets me SO much closer to fixing that incessant dinging!!! Now I just need to find time to start unwrapping the harness at or near point #11 on the diagram to find those wires...
 

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Discussion Starter #20
Ok, guys... Not quite done with this. I finally had the chance to look for the wires when I took out the intake manifold in order to replace the knock sensors (that is a big job for a car mechanic novice). All I could find was that the wires to the brake line pressure sensor were purple and black, and no other wires could be found. I have not gone under the truck yet to see if there are multiple purple wires coming off the EBCM (ABS controller). Can anyone verify the color of wires to the brake line pressure sensor?

Thank you,
csltrains96
 
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