Both the brake and ABS warning lights came on during a trip.
Motor home on a 2000, E-350 Super duty cutaway chassis. 119K miles.
Both front brake calipers were replaced before the trip. Approx 7000 miles traveled before the warning indicators lite up.
Cruise control, overdrive and speedometer are all working good
With key on the indicators light up as normal, after starting both lights go out then it sounds like a relay and they both come on to stay until shut down.
I've checked the resistance of both front wheel ABS sensors, each reads 2370.3 ohms on my ohmmeter.
I've checked out the E-brake switch and it's working properly.
What I don't understand is how to check out the brake fluid level sensor. There are 3 wires to this sensor (black, tan and green) so I'm not sure of how it operates.
Any information you have to pass on to me so I can continue to check it out will be greatly appreciated.

Thanks
Willey
.

 

Check the fluid level. The ABS light and the brake warning light will both go on when the fluid level is too low.

It could also be the float switch is bad, wiring, etc.

When the float switch says the level is low, the ABS system is disabled by removing power to it, and the light is lit.

 

"Both will go on" ah! piece of info I didn't have. The fluid level is fine right at the full line
Before going on the trip I removed some fluid as the shop filled it to the top after they replaced the calipers. I thought they just made a mistake but now I wonder. To be noted the fluid appears to me to be a bit dark & cloudy so as a test I may replace it with new fluid just to see if it makes a difference.
That's why I mentioned the three wires. This indicates to me that it's most likely a sensor rather than a simple on/off switch

Thanks this is more very important information I didn't have. I suspected that might be the case, but didn't know for sure. Hard to trouble shoot that way.
Guess I'll take a trip to the $ store for a turkey baster and the automotive store for a can of DOT 3
Thanks again
Cheers
Willey

 

Well I got the turkey baster and the new fluid and decided to learn about the level switch
There are three wires, (1 black); (2 tan) and (3 green). When the reservoir is empty the pins on the level switch that correspond to the above colored wires gave these results.
The # 1 wire shows a short to #2
when the reservoir is full #2 is shorted to #3 so it would appear that the fluid level switch is working ok.
Leaving the connector off and shorting pins 2 and 3 as would be normal for a correct fluid level still leaves both warning lights lighted.
Anyone have any more idea of where to look next ? I guess I'm wondering where the other ends of those wires connect to and I don't relish tearing the harness apart.

 

might be the abs tone ring sensor switch on top of the rear axle ... I've changed it on my e350 chassis RV and it solved the abs light problem you describe ... chock the wheels and crawl under the back ... disconnect the wire harness from the part on top of the axle ... use a 13mm wrench to loosen the bolt and pull it out vertically (screw driver might help) ... should look like a metallic dowel with a harness on top of it ... a new one is probably $11 ... crack open and beer and say 'kewl beans' - you just saved yourself a dealer repair bill of a few hundred smackers ....
johnniemac --->

 

easy folks take that big e250 down and get the codes checked and cleard

 

yeah but your post still hasn't answered his question ...

a code reader goes without saying ... I have my own as alot of mechanics do these days but this guy apparently doesn't have one and explaining how to jump the wires on the abs relay for a flashing dash light code is a tad over complicated for this post

its $100 in this area to have the st(d)ealer tell you the code (on an RV) and I'm guessing another $60 flat rate to install an $11 part ... my explanation should probably fix his issue in four minutes time for under $20 as it has countless other people on the web with the same recurring problem asking the same question about the same abs light on the same RV chassis ...

if the part doesn't darken the light than he can pay his mechanic to read the code and he knows he's got a new sensor ...

[.... and btw, WilleyB I forgot to ask: have you ever changed you rear axle fluid? the magnetic sensor might be full of filings causing it to incorrectly (?) read a problem which in itself might be THE problem (!) ..]

 

dosnt the computer store the trouble codes and if you dont remove them they keep comeing back?????

 

yes the computer stores the trouble codes; no you don't need a OBD code scanner to reset it; once you change the sensor you can remove the positive cable from your battery for fifteen seconds or so and it should reset the computer ...

BUT ... don't reset it just before you take it in for a yearly state inspection because the OBD computer won't have yet gathered enough info on the emissions for the state inspection computer to pass your truck and they will fail you and you have to come back ... it happened to me a few years back ...

I was told that you have to run the truck for something like 8 minutes or so at a minimum of 55mph or more following the battery disconnect to store enough emissions info to satisfy the state mongers who are watching over our rides... I just drove it daily and brought it back the following Saturday and it passed ... the abs code was gone ..

 

Hi Ken and thanks for your posts. Well yes I could go to the stealership for a code reading however that wont fix anything and it will cost $100 for the reading. Problem with that is if I didn't agree to fixing it right then and there theyed take the current safety sticker off and inform police, ah well nuts to that as the vehicle is as safe as it ever was. The ABS only deployed 0nce since I owned it (on a steep hill with new asphalt and a stop light ahead. (they do work but are not necessary if one knows how to drive)

Well yes, its a cheap enough fix if that (is or isn't) the problem. However the real problem is that any malfunction causing the brake light to be on will also shut down the ABS system and turn the ABS light on. I don't know if the rear sensor will cause the "brake" light to come on, but $11 is pretty cheap for a test so I'll try that first. The cruise control uses that sensor and it works OK.

I couldn't say for certain, as the rig is a Canadream ex rental that I bought in 2005. Canadream has their vehicles on a strict maintenance schedule for the warrantee requirements so I'd say it was done as per mfg's recommendations

Our safety inspections may not be as stringent as the ones you have, no emissions tests yet, or code reading. I've had the battery cable off so it isn't a stored code causing the lights to come on. If all else fails I'm building a logic circuit that will operate the lights as normal during the light and system check. One has to wonder though why Ford has chosen to turn the ABS light on/off with a large relay when the lead from the ECU that operates the relay would do the same thing for the light (strange?)

BTW folks All ideas welcome, does anyone know anything about the electronic control unit on the side of the HCU?

Cheers
Willey

 

great thread. i am having the same problem with my 2004 f250 4x4 diesel. i changed the master cylinder now my abs and brake light stay on. i keep thinking it's the sensor on the bottom of the reservoir for the brake fluid. don't see how it works (just a flat piece of plastic) but i may try to change it. everything was bench bled and brakes seem to be fine. fluid to the max line.

 

"(just a flat piece of plastic) but i may try to change it."

Just check it out with a continuity checker. Pins 1 & 2 black wire and brown wire terminals respectively will show a short if the fluid is too low or if the switch defective.

Willey

 

Well time for an up date. Late yesterday I discovered that the wire leading to the e-brake switch is shorted to ground, it was too late and too cold to pursue that further.

Today the following is what I found out, strange as it is I believe I'm going to find the trouble in the firewall connection plug or socket.

1 Normal e-brake switch disconnected dead short to ground on the wire. This wire
goes directly to the FW plug and is about 30 inches long at the most.

2 Disconnect other harness plugs going to the fire wall, the short remains

3 Disconnect the bottom plug (has e-brake lead) and short disappears
4 Measure resistance to ground from matching terminal on harness and it reads
about .5 Meg ohm far from being shorted
5 Re connect plug and short re appears when plug is seated with the securing screw.

Run out of time so will investigate more tomorrow weather permitting.

 

i ended up ohming out the 3 wire plug on the bottom of the reservoir. when there was fluid in the reservoir it switched one way. i pused the plunger down (inside the reservior)to simulate no fluid and it switched the other way on continuity. started the truck and drove it for a few miles and everything is fine! maybe i didn't give it enough time. i was just starting it in the driveway and couldn't get the abs and brake light to go off. all i did was change the brake master cylinder (that's when the lights came on). hope this helps someone having the same syptoms after changing this part.