Came across this and found it interesting reading. Ground connections can be a real hassle but you shouldn't ignore the opposite end of the circuit either. Depending on a person's training current flows from positive to negative (ground) or electrons flow from negative to positive. If the connections and wiring from the battery to the BPMV have a high resistance you will get the same result as if the motor itself has a high resistance or the ground connection has a high resistance.

Unplugging/plugging multicontact connectors can temporarily clean a voltage supply pin just as easily as it cleans the corresponding ground pin.

I suspect most of the relay failures probably aren't due to a high resistance but a lowered resistance. If the motor is turning slowly it will act like a low resistance or if the motor windings have conductivity to the motor case/ground more current will be pulled through the relay and more than likely will burn the relay contacts.


Bill

 

Yeah, I misspoke. By high resistance in the motor, I was really meaning to say resistance to turning freely, or mechanical drag. This spikes the current draw when the motor is energized. First time I hot-wired my motor it killed a 15 A fuse instantly. When it's loose after a few exercise runs, it only pulls about 4 amps.
One thing I have noticed when hot-wiring the motor: it will run smooth with low current draw for several seconds, then sometimes suddenly drag down.
I envisioned crud, rust, corrosion in the windings, bushings, or armature; but I wonder if maybe there is a set of gears in there that drive the pump impellers, and the drag is being produced there, not in the motor? I wonder if the brake fluid in the valve body (that doesn't get circulated or bled under normal procedures) could get nasty enough to create drag on the pump?
Same final results though: motor drags, kills itself or the relay.

DG

 

interesting read... so what would explain the 1242 (or 1243...i dont remember) code staying up for a month or so, and then NO ebcm codes... only "no comm"? the code seems to intuitively suggest that the module just isn't plugged in, but i highly don't that is the case, given the clip attached to it that secures it in place...

 

OK, you got me to read the manual.
My take on the codes 1242 and 1243, after pouring over the book is:

- 1242 looks for very very high resistance in the motor circuit, basically an open circuit greater than 6900 ohms. The open circuit could be caused by any connection; maybe from the fuse box, thru the EBCM, thru the relay in the EBCM, into the BPMV, into the motor brushes, or out thru the motor ground circuit. Somewhere (in the EBCM I assume) the computer reads the voltage drop or the current on the motor line when it is energized, and determines that it is highly resistive (very low current or no voltage drop). Obviously the motor would not run.

So, the procedure is to start at the chassis ground and work backwards thru the ground wire, into and thru the motor, to pin 8 on the BPMV which supplies the motor current, back to the relay in the
EBCM, etc.
Why did it heal? could have been resistive buildup on the motor brushes or the relay, could have been poor contact at pin 8 where the modules plug together.

-1243 is not too clear now that I thought about it. - it checks for a stalled or slow motor. This condition could be caused by either a resistive circuit (but less resistive than 6900 ohms) or it could be a mechanically seized motor (which would draw very high current if the circuit was not resistive).
So, opposite symptoms might set 1243? Either too little current, due to the resistive (but not open) circuit, or too much current, due to a seized motor? At low or zero RPM, a motor pulls a lot more current, and the computer may see this. There is a 40 amp fuse on the circuit, but the code sets before that current level is reached.
In my testing, the motor normally pulls about 4-5 amps, but I have seen mine suddenly spike to 10 amps and slow down for no reason.
Since the current is going up, I know it's not a circuit resistance problem, but something physically slowing the motor down - like crud or rust, etc. This increases the current draw as the motor loads down, putting stress on the relay points and the entire circuit.

That's how I interpret it anyway.

DG

 

And here I thought I was getting no responses - sorry I'm late. I made bold your comments about the connectors because I really believe it, now that I no longer see that 1242 code.

Wrench man, I hope you resolve your 1243 issue. It must be frustrating to say the least.

Dave

 

I've been fighting AH and TC faults for months. I followed Bill's advice and not only cleaned the grounds but cut all the ground modules off and soldered on lugs for a real ground. Took the ground splices and soldered all of those together. Also added the proper loading on the LED tail lights. I've had a constant "open Brake switch" fault since installing the LED mod even with a hyper flash module installed. Cleaned all the connections and pins at the EBTCM and re-spung the larger pins for good connections. Guess What! No more TC or AH faults. Take it from me - Do all that Bill suggest and I think 99% of our TC and AH faults will go away. It is really great to have such knowledge here on the forum to follow and utilize. I can not tell you how great it is to drive around without the little yellow car lighting up on the DIC. Thanks so much for all of your inputs Bill......I think alot of us try to make this to difficult. Just pull your faults and work both sides of the circuit. Make sure power side has proper voltage and ground side has proper (no resistace) ground. Amazing how it all comes together without changing a ton of parts just to get the same faults all over again. The EBTCM is extremley sensitive when it comes to correct B+ and grounds.