Several ABS codes

[JamesLond]

When you first start the car up, there's nothing, but after a minute or two of driving, the abs light comes on. It also feels like something is dragging. My scantool pulled these codes:

C0265
C0245
C0241
C0251
C0246
C0242
C0252

There's so many I don't know where to begin. I kind of think it might be electrical or ground related.

 

[rockola1971]

Likely bad solder joint inside your Electronic Brake Control Module.

C0245 Chevrolet: Code Meaning, Causes, Symptoms, & Tech Notes (With Video)

The Anti-Lock Brake System (ABS) relay supplies battery voltage to six valve solenoids. The Electronic Brake Control Module (EBCM) microprocessor applies

www.engine-codes.com

 

[JamesLond]

Does anyone know how to remove the ECBM connector? I got the red tab pulled down, but it ain't budging.

 

[Fless]

Have you tried pushing in where the arrow is, maybe gently with a screwdriver for a little more leverage to release the latch? Then pushing up on the connector a little to help relieve the pressure, then pulling the connector downward? I'm not sure if that works, but it might.

 

[JamesLond]

I ended separating the connector cover with a small screwdriver and pushing on that space below the green mark. It somehow made it easier and less rigid to push.

I then very carefully wiggled left to right while pulling the connector down.

A bunch of dried mud fell out after. This mud is just insidious on this car

I guess with it off now, would anyone know how to test the pins on the connector? The other one was simple since it's just power and ground and it tested OK.

 

[Pcpurvis]

I ended separating the connector cover with a small screwdriver and pushing on that space below the green mark. It somehow made it easier and less rigid to push.

I then very carefully wiggled left to right while pulling the connector down.

A bunch of dried mud fell out after. This mud is just insidious on this car

I guess with it off now, would anyone know how to test the pins on the connector? The other one was simple since it's just power and ground and it tested OK.

View attachment 366711

Can anyone confirm that this is the same pin out used on 2002 Yukon? Also for the 2002 Yukon is the B1 vehicle speed signal coming from the transmission speed sensor or is it actually from the rear wheel speed sensor? Reason I ask is that my launch CRP123 scan tool shows 3 wheel speed sensors for the 2002 Yukon and other web sites state that the rear wheel speed sensor is used as the vehicle speed sensor. I think that is bunk but what do I know?

Based on the above if I wanted to verify circuit continuity of the wheel speed sensors I should measure the VAC between B3 / A3 for the right wheel and B2/A2 for the left wheel (while spinning the wheels), correct?

Does anyone have a pinout reference or schematic of the PCM for the signals above? I would like to verify the PCN & ECBM have good connectivity.



Thanks in advance.

 

[MassHoe04]

Does your Yukon has stability control? I would guess probably, yes. But I am not the Yukon specialist.

Stability Control trucks appear to have 5 sensors (LF, RF, LR, RR + Transmission on the right rear).

My 04 w/o Stability Control has 3 (LF, RF + Transmission on right rear)

Here are both wiring diagrams from my 04 FSM... Hope it helps!

With Stability Control:



Without Stability Control:

 

[Pcpurvis]

Does your Yukon has stability control? I would guess probably, yes. But I am not the Yukon specialist.

Stability Control trucks appear to have 5 sensors (LF, RF, LR, RR + Transmission on the right rear).

My 04 w/o Stability Control has 3 (LF, RF + Transmission on right rear)

Here are both wiring diagrams from my 04 FSM... Hope it helps!

With Stability Control:
View attachment 394609


Without Stability Control:
View attachment 394611

Thanks for the diagrams; my 02 Yukon only has front wheel speed sensors. I replaced the brake pads and flushed the entire brake system with DOT4, cleaned the wheel sensors; I now have a firm brake peddle, great breaking power, and NO ABS / BRAKE codes! The ABS always worked even though it was throwing PO245 codes with the ABS / BRAKE warning lamps. Verified that power sliding on a dirt road.
What I believe was happening was that the old brake fluid along with the worn down pads was causing a brake sensor error into the ABS module. I paid extra attention to the bleeding procedure this last time to ensure no little air bubbles were present when compressing the brake peddle (used the 1 man bleeding method and a neat WiFi camera). Anyway, doing a complete brake job (greasing caliper pins, new ceramic pads, steel pad slides, new DOT4 flush, careful bleeding LR RR RF LF) did the trick. 3 days later +60 miles city driving and no issues.

Just thought I’d share that it wasn’t anything to do with a faulty ABS module. Wished I had known this before I removed it and resoldered the internal contacts; that is a risky repair- only do that if you have exhausted all other possible causes.

Chris

 

[MassHoe04]

Just to rule out one more thing 100% before closing the books on this...

Have you checked the hubs for excess play?
Excess slop in the hubs, just before the hubs fail, often start with no other noticeable symptoms other than ABS speed sensor codes.

Just for peace of mind, I would make sure the hubs are not worn.

 

[Pcpurvis]

Just to rule out one more thing 100% before closing the books on this...

Have you checked the hubs for excess play?
Excess slop in the hubs, just before the hubs fail, often start with no other noticeable symptoms other than ABS speed sensor codes.

Just for peace of mind, I would make sure the hubs are not worn.

Well I should have known the Gremlin King wouldn’t die that easy; the ABS warning lamp and Brake lamp are back. Intermittent with no commonality with speed or turning; some times just sitting still in park without the brake pedal depressed.

I did the bearing test and I believe both front bearings are good. But at 240000 miles they might be the first shot from the parts cannon.
I’ll replace the wheel speed sensors with the new hubs even though I believe they are good as well.

So is this the only way to approach this? I cleaned all grounds, verified circuit integrity (+12V,Gnd, speed sensors). I can activate the ABS (induced skid on a dirt road), replaced all brakes (they needed it), replaced the brake fluid with DOT4, bled the system (tight break pedal), pulled the unit and did the resolver job.
So let me know the best order to load and shoot the parts canon; ABS rebuild, wheel hubs, pCM??

Thanks