REAR ABS throwing Code #12
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Mountain Pass
Joined: Aug 2010
Posts: 225
Likes: 5
From: greater Zurich area
REAR ABS throwing Code #12
I'm trying to fix the RABS on my 97' Vulcan RWD right now, seems rocket-science to me. Having a Trouble Code #12 stored in KAM. So i was going thru the associated procedures 12.1 to 12.9:
All the "short to ground" related tests are negativ which leaves the Anti-Lock Electronic Control Modul as the only part that has to be replaced. Some of the Pinpoint tests i've performed as well, do ask for the Red Brake Light to be observed. I'm not shure what is meant with Red Brake Light: the one from the instrument cluster or the one in the tail lamp assembly? Last but not Least, recommended System Pre-Checks are including the Warning Lights from which the Brake Warning Light is one of them:
Confusione totalemente!
Cleaned the Vehicle Speed Sensor, tapped on Hydraulic Control Assembly with a small hammer.. yellow ABS light does the Self-Check and stays always On after, throwing the last stored Code #12 - any other thought on this?
Greets WB
- 12.1 CHECK WARNING LIGHTS
- 12.2 CHECK THE BRAKE FLUID LEVEL IN THE MASTER CYLINDER
- 12.3 VERIFY FLOAT BUOYANCY
- 12.4 CHECK CIRCUIT 531 (DG/Y) FOR A SHORT TO GROUND
- 12.5 CHECK THE DIODE/RESISTOR ELEMENT
- 12.6 CHECK CIRCUIT 512 (T/LG) FOR A SHORT TO GROUND
- 12.7 CHECK THE IGNITION SWITCH
- 12.8 CHECK THE BRAKE FLUID LEVEL SWITCH
- 12.9 CLEAR CODES/PULL CODES
All the "short to ground" related tests are negativ which leaves the Anti-Lock Electronic Control Modul as the only part that has to be replaced. Some of the Pinpoint tests i've performed as well, do ask for the Red Brake Light to be observed. I'm not shure what is meant with Red Brake Light: the one from the instrument cluster or the one in the tail lamp assembly? Last but not Least, recommended System Pre-Checks are including the Warning Lights from which the Brake Warning Light is one of them:
- The anti-lock electronic control module uses both the red BRAKE and yellow REAR ABS instrument panel warning lights to alert the driver to a system malfunction. Both lights must be working properly to assist in concern diagnosis.
Confusione totalemente!Cleaned the Vehicle Speed Sensor, tapped on Hydraulic Control Assembly with a small hammer.. yellow ABS light does the Self-Check and stays always On after, throwing the last stored Code #12 - any other thought on this?
Greets WB
Lead Driver
Joined: Sep 2003
Posts: 7,012
Likes: 204
From: SoCal
Did you check the rear brake lights, the ones in the tail light housing? You need to have someone look to make sure that they come on when you hit the brake pedal. If youdon't have an assistant, you will need to pull the bulbs out to check. I once got RABS warning light (and E4WD warning, and failed TC lock, and failed CC) from both rear brake light filaments burning out.
Thread Starter
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Mountain Pass
Joined: Aug 2010
Posts: 225
Likes: 5
From: greater Zurich area
Did you check the rear brake lights, the ones in the tail light housing? You need to have someone look to make sure that they come on when you hit the brake pedal. If youdon't have an assistant, you will need to pull the bulbs out to check. I once got RABS warning light (and E4WD warning, and failed TC lock, and failed CC) from both rear brake light filaments burning out.
Posting Guru
Joined: Jul 2004
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From: Mitchell, SD
Thread Starter
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Mountain Pass
Joined: Aug 2010
Posts: 225
Likes: 5
From: greater Zurich area
I did the: "Red Brake Light Off and Does Not Self-Check" Pinpoint Test
B1 - Red Brake Warning Light/Fuse = okay
B2 - Check For Corroded Fluid Level Connector Pins = okay
B3 - Check For Unseated Connector = okay
B4 - Diode Resistor Element/Circuit = DG/Y wire into MC Switch Harness Connector loose! Therefore no Brake Warning Light Self-Check..
B5 - Master Cylinder Fluid Level Switch = MC Fluid Level Switch defective! Jumper wire from DG/Y to T/LG (the wire next to DG/Y on MC Switch Harness Connector) simulates the "good condition" or the following in terms of the Wire Color Code corresponding to my Connector:
DG/Y______
T/LG______|_______/ ._____________Black
All i need to do now is replacing my MC because of the bad switch. Until that i leave it in "Jumper Mode".
cheers
Postmaster
Joined: Sep 2003
Posts: 4,452
Likes: 1
From: Southern California
You guys are getting weak. Back in the old days we would just open the door and stick our foot on the pavement to stop the car. Who needs brakes! 
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Postmaster
Joined: Apr 2001
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I had the same issue and wound up keeping mine in 'jumper mode' for a long time due to that simple switch problem. When I replaced the vacuum booster recently, I thoroughly cleaned out the MC reservoir until spotless and lo and behold - the switch works again! Might try that before buying a new MC.
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Mountain Pass
Joined: Aug 2010
Posts: 225
Likes: 5
From: greater Zurich area
Such a simple cause ... a loose wire and a bad switch ... it only can come better
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