ABS test Question?
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Junior User
Joined: Aug 2007
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From: New Brunswick Canada
ABS test Question?
My ABS is kicking in at slow speeds, here how I tested them.
Unhoocked front sensors and of course problem went away but when I unhooked only left and then only right the problem didn't occur. Does this eliminate the front sensors and maybe it's the back, or am I on the wrong track?
ps, got ohms reading on all sensor, forget what they were though.
Unhoocked front sensors and of course problem went away but when I unhooked only left and then only right the problem didn't occur. Does this eliminate the front sensors and maybe it's the back, or am I on the wrong track?
ps, got ohms reading on all sensor, forget what they were though.
Lead Driver
Joined: Sep 2006
Posts: 7,907
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You normally can't do testing in that manner because it may disable the ABS function .
This is because if one wheel ABS was inoperative and the system were left to function the ABS and something happened, the truck would be worse off than without any ABS function. Same as if one wheel locked with normal braking causing the truck to turn/pull out of control from one wheel lockup or loss of traction without the other to have some balance, countering it..
What you might have is a 'rub-thru' on one sensor cable that falsely signals the control module to invoke ABS and kicking the brake pedal or running the motor.
A rear sensor faulty.
This is because if one wheel ABS was inoperative and the system were left to function the ABS and something happened, the truck would be worse off than without any ABS function. Same as if one wheel locked with normal braking causing the truck to turn/pull out of control from one wheel lockup or loss of traction without the other to have some balance, countering it..
What you might have is a 'rub-thru' on one sensor cable that falsely signals the control module to invoke ABS and kicking the brake pedal or running the motor.
A rear sensor faulty.
Hotshot
Joined: Jan 2004
Posts: 19,736
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From: St Louis
Identify which vehicle you're working on. we are not psychic.
As Bluegrass mentioned, your test procedure is invalid. Unplugging any sensor causes the system to be forced off line and leaves you with your standard hydraulic brakes with NO ABS assist.
You need to get the system scanned to see if there are an stored fault codes.
Otherwise, here's the intro to the diagnostic that most likely describes your concern:
o ABS Misfire, ABS Too Sensitive, ABS Fires On Normal Stop
Possible Source(s):
§ Rear anti-lock brake sensor indicator is damaged.
Action(s) to take:
§ REMOVE rear sensor from the differential housing; INSPECT rear anti-lock brake sensor indicator.
Possible Source(s):
§ Front anti-lock brake sensor indicator is damaged.
Action(s) to take:
§ INSPECT for damaged teeth. INSPECT both front tone rings.
Possible Source(s):
§ Sensor output is out of sync.
Action(s) to take:
§ If left front sensor output is out of sync, GO to «Pinpoint Test F». If right front sensor output is out of sync, GO to «Pinpoint Test H». If rear sensor output is out of sync, GO to «Pinpoint Test J».
Possible Source(s):
§ Intermittent open or shorted sensor circuit.
Action(s) to take:
§ GO to Intermittent Failures to test circuits: 514 (YE/RD), 516 (YE/BK), 523 (RD/PK) and 519 (LG/BK).
Possible Source(s):
§ Chafed wire insulation or pinched wire due to improper routing causing intermittent short.
Action(s) to take:
§ INSPECT wiring harness from front sensor knuckle to the frame and from the rear axle to the frame for worn or chafed wire insulation.
Possible Source(s):
§ Rear brake adjustment too tight.
§ Linings are grabby.
Action(s) to take:
§ ELIMINATE base brake system as cause of problem.
Possible Source(s):
§ Loose sensor(s).
Action(s) to take:
§ TIGHTEN sensor bolt to specifications. REFER to Specifications.
Has any recent front brake or suspension work been done?
Steve
As Bluegrass mentioned, your test procedure is invalid. Unplugging any sensor causes the system to be forced off line and leaves you with your standard hydraulic brakes with NO ABS assist.
You need to get the system scanned to see if there are an stored fault codes.
Otherwise, here's the intro to the diagnostic that most likely describes your concern:
o ABS Misfire, ABS Too Sensitive, ABS Fires On Normal Stop
Possible Source(s):
§ Rear anti-lock brake sensor indicator is damaged.
Action(s) to take:
§ REMOVE rear sensor from the differential housing; INSPECT rear anti-lock brake sensor indicator.
Possible Source(s):
§ Front anti-lock brake sensor indicator is damaged.
Action(s) to take:
§ INSPECT for damaged teeth. INSPECT both front tone rings.
Possible Source(s):
§ Sensor output is out of sync.
Action(s) to take:
§ If left front sensor output is out of sync, GO to «Pinpoint Test F». If right front sensor output is out of sync, GO to «Pinpoint Test H». If rear sensor output is out of sync, GO to «Pinpoint Test J».
Possible Source(s):
§ Intermittent open or shorted sensor circuit.
Action(s) to take:
§ GO to Intermittent Failures to test circuits: 514 (YE/RD), 516 (YE/BK), 523 (RD/PK) and 519 (LG/BK).
Possible Source(s):
§ Chafed wire insulation or pinched wire due to improper routing causing intermittent short.
Action(s) to take:
§ INSPECT wiring harness from front sensor knuckle to the frame and from the rear axle to the frame for worn or chafed wire insulation.
Possible Source(s):
§ Rear brake adjustment too tight.
§ Linings are grabby.
Action(s) to take:
§ ELIMINATE base brake system as cause of problem.
Possible Source(s):
§ Loose sensor(s).
Action(s) to take:
§ TIGHTEN sensor bolt to specifications. REFER to Specifications.
Steve
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Junior User
Joined: Aug 2007
Posts: 70
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From: New Brunswick Canada
Thanks Bluegras I figure I was on the wrong path. I inspected every sensor all look fine, time for code reading, wish I were psychic like Projectsho and I would know what was wrong, chow for now
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