88 Rear Antilock code 2: 'Open Isolate Circuit'
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Cargo Master
Joined: Jul 2000
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From: Northern California
88 Rear Antilock code 2: 'Open Isolate Circuit'
I have an 88 F350 w/rear antilock. The dash light is on, has been for a long time. The code reads 2 (one short flash, one long flash).
The books says this is an 'Open isolate circuit'. Does that mean that one of the wires is not connected? Is the 'isolate circuit' a sub part of the brake system and is that where the short / break is?
Any help would be great, thanks KarlJay.
The books says this is an 'Open isolate circuit'. Does that mean that one of the wires is not connected? Is the 'isolate circuit' a sub part of the brake system and is that where the short / break is?
Any help would be great, thanks KarlJay.
Senior User
Joined: Jul 2009
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If that is the correct code,there is three parts to it 2a 2b 2c.It can be a long diagnosis process.Go to this web site and you can find many different pin point test and much more for your truck..It will cost you 17 dollars for a year but well worth it to the DIYer..Good Luck.. http://www.alldatadiy.com/
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Cargo Master
Joined: Jul 2000
Posts: 2,281
Likes: 18
From: Northern California
OK, looks like it's also know as:
2 Open Isolate circuit (In RABS Isolate/Dump valve)
So has anyone delt with this before?
Does it need to be reset or something?
I know it has a bleader valve on it. is there a special way to bleed these brakes?
2 Open Isolate circuit (In RABS Isolate/Dump valve)
So has anyone delt with this before?
Does it need to be reset or something?
I know it has a bleader valve on it. is there a special way to bleed these brakes?
Senior User
Joined: Jul 2009
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These trucks are light in the rear end,the Brakes can lock up easy in the rain thats why it has the RABS..If you pull up your truck on the web site above it will give you many pin point test to narrow it down.. The culprit is usually the Hydraulic Unit or Rear Speed Sensor..I have replaced tons of them over the years..The hydraulic unit is about $140 and the speed sensor is $20..But i would spend the $17 on Alldata first to diagnose it.
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Cargo Master
Joined: Jul 2000
Posts: 2,281
Likes: 18
From: Northern California
YEA, the pedal did sink... is there a way to just bypass the anti lock, because it sounds like something I can live without. I don't have anti lock on anything else, but I'm concerned about lockups. I was thinking of a bias valve that would give more pressure to the front brakes, the adjustable ones are only about $50.
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Post Fiend
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YEA, the pedal did sink... is there a way to just bypass the anti lock, because it sounds like something I can live without. I don't have anti lock on anything else, but I'm concerned about lockups. I was thinking of a bias valve that would give more pressure to the front brakes, the adjustable ones are only about $50.
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Fleet Owner
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From: southern md
There is an easy way to bypass the dunp circuit in the RABS module. You will see a large hex bung on the front of the module, unscrew it against the spring pressure and remove the spring (no fluid will come out). Replace the bung. Pump the pedal a few times to fill the chamber and the sinking pedal should be gone. You can restore the module to original again simply by replacing the spring. I drove mine for four years with the spring out and it was great not to have the pedal sink at lights.
(crosses fingers)
Post Fiend
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Thank you. That only works if the problem is with the dump solenoid, the bypass pipe would be needed if the problem was something else such as fluid not returning from the rear brakes.
Post Fiend
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Well, if you go to autozone.com and register with the repair section (free) you can get free access to a lot of alldata.
However for open dump valve circuit probably the solenoid valve inside the RABS Hydraulic Control Module is bad or the wiring pigtail to it is bad.
You will get plenty of info on the system if you google kelsey-hayes rabs or kelsey-hayes rwal. Also good info at raybestos.com in the training section.
However for open dump valve circuit probably the solenoid valve inside the RABS Hydraulic Control Module is bad or the wiring pigtail to it is bad.
You will get plenty of info on the system if you google kelsey-hayes rabs or kelsey-hayes rwal. Also good info at raybestos.com in the training section.
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