ABS DTC code 51 (1 Viewer)
- Thread starter lt403
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Closing out this thread for myself and any future searchers.
Shout out to @slow95z. He got me the used ABS controller quickly and as advertised for a good price.
Installation was pretty simple. There are always the corrosive concerns whenever working with DOT3 fluid. Bleeding was more of a challenge as no fluid was moving initially. I correctly figured I needed to activate the ABS controller to start the fluid flow. I used the jack stand method in this old thread Is there a way to trigger ABS actuator to combat spongy breakes?. From there, bleeding was straight forward.
That same thread gives you the wiring diagram to manually activate the ABS controller using jumper wires. I was asking about that capability earlier in this thread, so I thought I'd give it a go on my old ABS controller and see if that got it working. Nope. Dead as a doornail. So the ABS code 51 seems to be a legitimate indication the ABS controller is dead.
ABS is back functioning properly with no more codes. Thanks for the help everyone.
Shout out to @slow95z. He got me the used ABS controller quickly and as advertised for a good price.
Installation was pretty simple. There are always the corrosive concerns whenever working with DOT3 fluid. Bleeding was more of a challenge as no fluid was moving initially. I correctly figured I needed to activate the ABS controller to start the fluid flow. I used the jack stand method in this old thread Is there a way to trigger ABS actuator to combat spongy breakes?. From there, bleeding was straight forward.
That same thread gives you the wiring diagram to manually activate the ABS controller using jumper wires. I was asking about that capability earlier in this thread, so I thought I'd give it a go on my old ABS controller and see if that got it working. Nope. Dead as a doornail. So the ABS code 51 seems to be a legitimate indication the ABS controller is dead.
ABS is back functioning properly with no more codes. Thanks for the help everyone.
I am also getting a code 51 and have been cleaning ground connections throughout. I also upgraded the grounds from the battery with no luck. I'll be (hopefully) getting an ABS motor and will let you know what the results are.
You could try hot wiring it, like the link in post 23 describes. That creates new grounds. In my case, I just got a big spark jump with the connectIon to the battery. No solenoid engagement. However, no one on this thread seems to have solved the code 51 without replacing the controller.
Good luck.
Good luck.
My personal opinion is because the brushes like on every electric motor eventually wear out. The code indicates a stuck pump motor. If the motor shaft isn't spinning it's either jammed, or there's no field pushing through the armature. As I said in a previous commitment I thought there was someone rebuilding the motors. Seems like a good niche to get into. Especially with the age of some of these vehicles out there. It's only a matter of time before everyone will need it done.
What's odd is in the diagnostic manual I came across online, Code 51 had two parts to it. If the buzzer was on and the light was on then the pump motor was locked. However, if only the light was on, according to the manual, the problem lay in the MT+ or MT- harness. (Not sure what MT refers to but assume it's referring to pos and neg wires in ABS system)
@hobbes Was your buzzer on when you had the code?
@hobbes Was your buzzer on when you had the code?
I'm also unsure of which buzzer it's referring to. The link I had is now dead, or else I would post it up. Let me see if I can find it...
I think I could hear a slight humming on mine when I jumped it. Motor was probably locked. I've got my old one sitting in a box. Not sure if I want to toss it or not.
I've been unable to find that diagnostic sheet I was looking at, but here's another thing to consider.
The PO installed a new booster and master cylinder a month before I purchased the vehicle (everything has been performed by the dealer for the past 25 years). He said the ABS line came on right after he had those replaced. So, I'm wondering if when the car was bled it dislodged some gunk in the lines causing the ABS pump to lock. I have a used one on the way, but am thinking a purge from the link you provided may help.
Thoughts on the connection between a new master cylinder and a Code 51 coming on right after it's replaced?
The PO installed a new booster and master cylinder a month before I purchased the vehicle (everything has been performed by the dealer for the past 25 years). He said the ABS line came on right after he had those replaced. So, I'm wondering if when the car was bled it dislodged some gunk in the lines causing the ABS pump to lock. I have a used one on the way, but am thinking a purge from the link you provided may help.
Thoughts on the connection between a new master cylinder and a Code 51 coming on right after it's replaced?
Mine occurred right after I did some front axle work. I was convinced when the light came on it was due to that. Turns out that was an incorrect assumption in my case. I don’t know why changing a master/booster would cause a 51 code. Perhaps if they actuated it to bleed the brakes that was coincidentally it’s last gasp?
Just want to confirm that replacing the ABS pump with a used pump SOLVED the ABS Code 51 for me. Was pretty easy to bleed and besides one of the ABS lines needing to be torched to loosen up, went smoothly.
I wanted to share a relatively easy fix for code 51 that may apply in some situations. On my '97 I noticed the ABS light earlier today and pulled the codes after a general inspection and test of the CDL, etc. The code that came back was 51 so I then hot-wired the abs pump to see if it would turn over with direct power applied. This is something that I do during brake bleeding so I was familiar with how the pump should sound. When I hot-wired the pump the sound/feel of the pump lead me to believe that motor was ok electrically but blocked mechanically, which turned out to be the case.
I pulled the ABS pump and then removed the electrical motor housing which revealed rust scale that had lodged between the magnets and motors armature, thus physically locking the motor. There's a picture below of the cover after removal and before cleaning.
I cleaned the rust out, applied rust converter then re-assembled and installed the pump which works fine again. Hardest parts of the job were probably getting the rust scale out, which was sticking because of the the housing being magnetic, and then of course bleeding the brakes which always seems to take me a few large bottles of fluid before the pedal feels right again.
I pulled the ABS pump and then removed the electrical motor housing which revealed rust scale that had lodged between the magnets and motors armature, thus physically locking the motor. There's a picture below of the cover after removal and before cleaning.
I cleaned the rust out, applied rust converter then re-assembled and installed the pump which works fine again. Hardest parts of the job were probably getting the rust scale out, which was sticking because of the the housing being magnetic, and then of course bleeding the brakes which always seems to take me a few large bottles of fluid before the pedal feels right again.
Rust is caused by condensation and if someone decides to use a pressure washer on the abs pump. There is a weep hole on the bottom. Most of the ones I've taken apart look like yours except it's not the magnet that gets in the way it's the metal plate they use for mounting the brushes. This rots out and deforms and eventually shorts out what I believe is a thermal fuse. Had they made those plates from stainless or brass we wouldn't be having any issues. Usually the brushes have a ton of life left in them.
JPoole, Nice fix, How did you hold the brushes back into their slots when re-installing the armature? Seems like that would be a major PIA.
There's a small round cover that provides direct access to the brushes. I don't recall exactly how I assembled it but I assume I rolled a thin sheet of plastic or cardboard into a tube that fit over the end of the armature and through the access hole and then used that tube to hold the brushes out while I slid the armature into the cover. Once that's done I assume I slipped the tube out to allow the brushes to click against the armature and then popped the access cover back on. I'm pretty sure it was a very easy re-assembly once the rust was removed.
So I currently have 2 yes 2 twin 1995 FZJ80's that I am working on with exactly the same ABS 51 code and ironically the same SRS 11, 12, 31 codes...go figure but lets stick to the ABS issue which is what this thread was about. I used the jumper method to try and excite the ABS motor on both of these trucks and I only got a solenoid click on one post and nothing on the other. leading me to believe I have a locked or bad ABS motor on both of these trucks. Additionally I have a 93 rusty parts truck that is still intact and running so I went out there and performed the same test on that truck and that one I got the motor to spin. only difference is that that one is empty on fluid due to a rusted out brake line so I wonder if lack of fluid lets the motor spin, @jpoole did your motor spin over even when full of fluid and bled out? I'm thinking I at least have a good ABS unit I can swap over to one of these trucks but don't want to mess with it until I'm sure that's the culprit, Both run great, start, stop, etc, so I don't want to tear into it till I need to. I may go ahead and obtain a used one as well, Have you ever bench tested one to get it spinning using the jumper method from a 12v source. I don't see why it wouldn't work.
These abs pump spin when full of fluid, bled free of air and then jumped. I primarily use the jump method to activate the pump during bleeding cycles as one of many steps to try to please the 80 series brake gods enough to let all of the air out of the system.
I don't have a ton of experience with these pumps but I'd lean towards checking / fixing the ones that have had fluid in them over ones that have been open as I'd be concerned about internal corrosion. You could get moisture in a closed or open system and I don't really know what's going to present the greatest likelihood of damage to one of these but it's something to consider.
good luck
I don't have a ton of experience with these pumps but I'd lean towards checking / fixing the ones that have had fluid in them over ones that have been open as I'd be concerned about internal corrosion. You could get moisture in a closed or open system and I don't really know what's going to present the greatest likelihood of damage to one of these but it's something to consider.
good luck
