2014 Ram 3500 6.4 Brake Sensor Codes

The automatic transmission, 66RFE, went out. I replaced the trans and cleared all codes. It will not let me perform the quick relearn because of codes in the PCM. With codes cleared I immediately get a P1C4E ABS DTC Present when I press the brake pedal. In the ABS module I get C0042-12 Brake Pedal Position Sensor - Circuit Short To Battery, and C1223-01 Brake Pedal Travel Sensor Supply - General Electrical Failure. I replaced the brake pedal sensor, thinking quick fix, with no change. In the scan tool I read .5v-3.5v with a smooth reading as I move the brake pedal. I have not done any back probing yet on connectors but will early next weel. It is odd that I am getting these codes when the ABS module is reporting proper voltage. Any thought on this would be greatly appreciated.

FWIW, I'd follow the C1223 first. Service info seems to be fairly specific on the set criteria:

When the Anti-lock Brake System (ABS) Module detects that the Brake Pedal Position (BPP) Sensor is indicating less than 4.75 volts or greater than 5.25 volts for more than 500 msec.

Depending on how hard the BPP sensor is to access, I might go directly to the ABS module instead. The ABS connector is easy-ish to access once you've got the right front fender liner out of the way.

I've tested all three wires in the circuit for short to power or ground and have no shorts or opens. According to Pro Demand, at the sensor terminal 1 is sensor return, terminal 2 is sensor feed, and terminal 3 is sensor signal. With the sensor disconnected I have 5v on terminal 3 and no voltage on the other two. When I back probe with the sensor connected, I never have voltage on terminal 1, terminal 2 starts at 0.5v and travels up to 3.7v and then jumps to 10.8v, terminal 3 stays at 5v until I hit the point where terminal 2 jumps to 10.8v then terminal 3 jumps to 5.8v.

In the ag world a three wire potentiometer has power, ground and signal. The signal terminal sends the variable voltage back to the control module. In my mind terminal 3, which is sensor signal, should have the variable voltage and not terminal 2 which is sensor feed. Am I correct on this or am I misinterpreting the diagram? I also ohmed out the wires to make sure the proper terminals are connected between the sensor and the ABS module which show to be correct according to the diagram.

fixn_junk wrote:

According to Pro Demand, at the sensor terminal 1 is sensor return, terminal 2 is sensor feed, and terminal 3 is sensor signal...am I misinterpreting the diagram?

I believe that diagram is wrong.

Here is a snippet from the OE diagram:

Thank you. That make sense. Something that's been bugging me is the point where the signal voltage jumps to 10.8 and the sensor feed jumps to 5.8. Seeing that the circuit checked out, wouldn't this suggest an issue with the ABS module? There should never be more than 5v at the BPP sensor at any time on any terminal.

fixn_junk wrote:

When I back probe with the sensor connected, I never have voltage on terminal 1, terminal 2 starts at 0.5v and travels up to 3.7v and then jumps to 10.8v, terminal 3 stays at 5v until I hit the point where terminal 2 jumps to 10.8v then terminal 3 jumps to 5.8v

If you are certain that the signal wire is not shorted to power, external of the ABS module, during the moments that voltage jumps to 10.8 volts, then I would be confident in replacing the module.

Before I did, though, I would smack the module around, a little bit. Not only to show it who's boss, but to see if I could induce some voltage spikes on the signal wire, by doing so.

terminal 2 starts at 0.5v and travels up to 3.7v and then jumps to 10.8v, terminal 3 stays at 5v until I hit the point where terminal 2 jumps to 10.8v then terminal 3 jumps to 5.8v.

Is this repeatable, every time?

Yes. Every time I cycle the brake pedal.

Also, I disconnected the ABS module and the BPP sensor checking for voltage on all three wires with the key on and had no voltage on any of the wires. It seems voltage induced as I perform the test KOEO and it repeats 100% of the time.

I would also make sure to do all of the necessary testing for C1223, as Tyler suggested.

C1223

I've gone through all of it several times. I've trained myself over the years that when diagnostic aids say to replace the module, I say it's not the module and retest. I'm at the point where my gut feeling is it's the module but I'm not overly confident as I am far less experienced in the auto world. The only other thing in the back of my mind is, being pretty unfamiliar with everything involved with the ABS module, I'm wondering if there's any possibility that something else in the system could be messing with the module when the voltage hits 3.7. It's really odd to me how precisely this can be replicated. I have it partially raised on the hoist for best access to the module and sensor so I'm applying with my hand and very slowly. Every single time I cycle the pedal, it happens at 3.7v with a variance of at most .03v and every time it jumps to exactly 10.8v with about the same variance. Also, the supply voltage jumps slightly to 5.8v so the excessive voltage has to be back feeding through the module.

I just got to thinking I probably have low voltage by now so I tested it KOER. Signal terminal goes to 2v and then jumps to battery voltage, 13.5, and the supply voltage jumps to 7.5.

I ran through the tests again. The final test is plug the module in turn the key on and check voltage between sensor supply and return. The required voltage is 4.75 or above. I have 5v with the key on and off. 5v supply shouldn't be available key off should it?


Disregard. It just dawned on me the module hadn't gone to sleep yet. Voltage is gone. Is it possible that if I didn't properly initialize the new switch, it could be causing all of this? My scanner doesn't give me much information on that particular process, but it appears to be completed.

I am back to the module. I can't find any other reason I would get to battery voltage on the signal terminal with 5.8 on the supply except something is shorting in the module. My scanner has all of the initialization processes in it. Can I replace the module or does it have to be dealer programmed?

Sorry for the delayed response, life has been pretty crazy here lately. I appreciate all of the input and I did resolve my issue. I wanted to get this out there as I'm sure this is an issue on more of these pickups and probably not realized yet in many cases. I did end up finding wires rubbed through where the harness containing the ABS wiring passes by the power steering reservoir. The hose on the bottom of the reservoir rubbed through the insulation on several wires. I apparently had one strand lightly contacting the hot wire. It never showed up in a voltage test or and ohm test but, looking back, I think a load test would have shown something on the little wires going to the brake pedal sensor as much ware as there was. With the fender splash guard out it didn't look like the harness was in contact with the hose at all. I actually found it when I disconnected the ground right below on the frame and pulled it back. You have to pull the harness back to see the abrasion. I have attached a picture of the problem area. I didn't get a good angle on the abrasion but you can see bare wire.