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Discussion Starter · #1 ·
I have checked the brakes they are fine,Took car in they said the fault was low brake fluid sensor which is in the master cylinder so I let them change it,Didn't help they said it was defective so they changed it.Still have the problem It's driving me crazy,Won't allow cruise to operate.Does anyone have a fix.
 

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IF you or a friend, have access to a multi-meter an want to perform a little troubleshooting, I can post up some testing that would allow you to verify the condition of the power an ground wires used in that low fluid level brake circuit. This to allow you to either verify it as the cause, or eliminate it. But if you are the type that takes it to a shop, I'll leave it up to you an the shop.
 

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Discussion Starter · #4 ·
I would love to give it a try,I have a decent meter.Not a Harbor Freight one,I'd rather do it myself when possible.
 

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If you disconnect the sensor does the light go out?
 

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Disconnecting the sensor would trip it as a fault. The sensor should show no power when the fluid level is good.

Unplugging it would trip it as a broken circuit.

Do you apply the parking brake? Check there, if you do there can be an issue there that would also trip the brake light.

I don't remember since I have not driven my GXP in a long time.
 

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Thinking if the parking brake circuitry or etc. were the issue, the driver information center would display park brake or something to that end in addition to the brake light indicator on the instrument cluster.
 

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Discussion Starter · #8 ·
Disconnecting the sensor would trip it as a fault. The sensor should show no power when the fluid level is good.

Unplugging it would trip it as a broken circuit.

Do you apply the parking brake? Check there, if you do there can be an issue there that would also trip the brake light.

I don't remember since I have not driven my GXP in a long time.
I don't use the parking brake,And the break lights work so I dont think it's the brake light switch.
 

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You sure make it tough on your transmissions parking pawl, never using that parking brake for what its purpose is for. IF at anytime the brake light is off (with ignition on), cycle that (never used) parking brake handle. If the BRAKE light in the cluster cycles on an off, your parking brake circuit can be eliminated.
If you want to attack the low level sensor circuit do this >>>>> Unbolt the bracket supporting your alarm horn, an move it as necessary to gain better access to the brake reservoir low level switch connector. If you still have the connector lock clip in place (a C shaped thin wire), pry it upwards a little bit to force the tabs outwards that are currently recessed into the sides of the connector. That will allow you to pull the connector back at you an remove for troubleshooting.

At a time when the BRAKE light is on (an it should not be), install a jump wire between the 2 pins of the connector, turn the ignition on, an see if the light turns off. If it does not happen, remove the jump wire an do whats posted next.

With the meter set for DC voltage, turn on the ignition an verify that about 4.8 volts (plus or minus a little) is read at the multi color wire terminal, with the other lead contacting the ground stud at the underhood jump start location. If OK, turn the ignition off. Change to read resistance an connect one lead to the black wire terminal, an the other lead to that same ground. You must show continuity (very close to zero ohms). Answers will dictate what might/must be wrong
 

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Discussion Starter · #10 ·
You sure make it tough on your transmissions parking pawl, never using that parking brake for what its purpose is for. IF at anytime the brake light is off (with ignition on), cycle that (never used) parking brake handle. If the BRAKE light in the cluster cycles on an off, your parking brake circuit can be eliminated.
If you want to attack the low level sensor circuit do this >>>>> Unbolt the bracket supporting your alarm horn, an move it as necessary to gain better access to the brake reservoir low level switch connector. If you still have the connector lock clip in place (a C shaped thin wire), pry it upwards a little bit to force the tabs outwards that are currently recessed into the sides of the connector. That will allow you to pull the connector back at you an remove for troubleshooting.

At a time when the BRAKE light is on (an it should not be), install a jump wire between the 2 pins of the connector, turn the ignition on, an see if the light turns off. If it does not happen, remove the jump wire an do whats posted next.

With the meter set for DC voltage, turn on the ignition an verify that about 4.8 volts (plus or minus a little) is read at the multi color wire terminal, with the other lead contacting the ground stud at the underhood jump start location. If OK, turn the ignition off. Change to read resistance an connect one lead to the black wire terminal, an the other lead to that same ground. You must show continuity (very close to zero ohms). Answers will dictate what might/must be wrong
I'll try that in the morning Thank you.
You sure make it tough on your transmissions parking pawl, never using that parking brake for what its purpose is for. IF at anytime the brake light is off (with ignition on), cycle that (never used) parking brake handle. If the BRAKE light in the cluster cycles on an off, your parking brake circuit can be eliminated.
If you want to attack the low level sensor circuit do this >>>>> Unbolt the bracket supporting your alarm horn, an move it as necessary to gain better access to the brake reservoir low level switch connector. If you still have the connector lock clip in place (a C shaped thin wire), pry it upwards a little bit to force the tabs outwards that are currently recessed into the sides of the connector. That will allow you to pull the connector back at you an remove for troubleshooting.

At a time when the BRAKE light is on (an it should not be), install a jump wire between the 2 pins of the connector, turn the ignition on, an see if the light turns off. If it does not happen, remove the jump wire an do whats posted next.

With the meter set for DC voltage, turn on the ignition an verify that about 4.8 volts (plus or minus a little) is read at the multi color wire terminal, with the other lead contacting the ground stud at the underhood jump start location. If OK, turn the ignition off. Change to read resistance an connect one lead to the black wire terminal, an the other lead to that same ground. You must show continuity (very close to zero ohms). Answers will dictate what might/must be wrong
My wife drove the car today,She had to slam on the brakes faut went away but came back,Any idea's about that.
 

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The 3rd item that can produce the BRAKE icon to illuminate, is when a problem with the EBD (electronic brake distribution) circuit goes haywire. Its purpose (as best as I can understand), is to modify the bias pressure to the rear brakes when necessary. Have never read over the years, of anybody actually having that circuit fail. An,you would never want it to fail due to it being a function of the "Electronic Brake Control Module (super big bucks item to R&R.

I'll wait for a post on what you find, performing the T/S posted for the low level sensor circuit. Remembering that the BRAKE icon has to be on when T/S to best locate the problem (if this is in fact, the faulty circuit).
 

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Disconnecting the sensor would trip it as a fault. The sensor should show no power when the fluid level is good.

Unplugging it would trip it as a broken circuit.

Do you apply the parking brake? Check there, if you do there can be an issue there that would also trip the brake light.

I don't remember since I have not driven my GXP in a long time.
Jump the wire then to eliminate the switch?
 

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So I just had to diagnose and fix a BRAKE light/ DIC BRAKE WARNING on my newly acquired G8 base. What I discovered is that there are only two items that typically would cause strictly the red BRAKE light and/or warning in the DIC to come on: the park brake switch (which will strictly result in just the [BRAKE] light coming on unless you're moving) and the fluid reservoir switch. I believe the EBD that member GOPHERIT cited will cause the ABS light to come on as well, according to the service data I have (Alldata). All other braking/ TCS faults will cause either the ABS or both ABS/ BRAKE warnings to appear. Anyway, in my case it was the brake fluid level circuit. The instrument cluster sends 5 volts down to the level sensor, which when full, will "ground" to chassis ground. I put ground in quotes because the fluid level sensor will read approximately 10k OHM when full, and open circuit when fluid level is low. Thus, simply unplugging or shorting the connector WILL NOT eliminate the brake warning. I tested this by jumping the 5V wire to ground with a 10k resistor, and the light promptly turned off. I had 5V to the sensor, but no good ground (won't light a test light/ open circuit when checking resistance). Wiring diagrams indicate its grounded at G102, but that spot is good (I checked it and cleaned it) and is also shared with a myriad of other components, so I have a broken wire somewhere in the harness.
 

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^^^^^^^ Does this mean that if you install a jump wire from the connectors 5 volt pin straight to ground, the BRAKE light would remain illuminated, but if that same jump wire attached to the 5 volt pin to ground had a resistance value of 10K ohms, it would cancel the light ? Or any jump wire value at "10K or less" would work ?
 

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Repair ground at under hood fuse box connector behind box, or jump new ground to sensor, what most don't know is it is a feedback system from ground through sensor to cluster, the sensor loses its ground at box connector when pins corrode, it is not like on or off as a conventional switch, just add a ground to sensor wire ground at pin 1 black wire of sensor
 

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Discussion Starter · #16 ·
I tried jumping at connector to M.Cyl.I will try at the box.Checked with ohm meter open.
 

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^^^^^^^ Does this mean that if you install a jump wire from the connectors 5 volt pin straight to ground, the BRAKE light would remain illuminated, but if that same jump wire attached to the 5 volt pin to ground had a resistance value of 10K ohms, it would cancel the light ? Or any jump wire value at "10K or less" would work ?
Sorry I didn't respond sooner. I apparently don't receive notifications for threads. Anyway, you would be correct that shorting the 5v REF to ground will keep the brake warning illuminated. The resistance value has a certain tolerance, likely +/- 5%, so it has to be within that range of 10k Ohm. I just used a resistor to check for circuit integrity and to rule out the fluid level sensor being bad.
 

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Sorry I didn't respond sooner. I apparently don't receive notifications for threads...
Click/hoover on avatar. Account settings. Preferences. Check the box to activate. Save.
 
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