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Discussion Starter #1
The brakes seem to be working OK otherwise.

Any help is much appreciated.
 

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Not sure if the '94 is the same as '95 but FWIW..

Diagnostic Process
If a visual inspection does not reveal the cause of the malfunction, perform the "Functional Test". Always start with Functional Test. This is a critical step in the quick and and accurate diagnosis of any malfunction. It will direct you to specific system area that is malfunctioning and verify that the diagnostic system is functioning properly. Correct system diagnosis cant be ensured without starting diagnosis with the Functional Test.

Displaying Diagnostic Trouble Codes
ABS DTCs can be read with a scan tool or by jumping DLC terminal "A" to DLC terminal "H" and counting the flashing "Antilock" lamp flashes much like counting MIL flashes for ECM/PCM DTCs..

Clearing ABS DTCs
If "Antilock" indicator lamp is staying on, the DTCs can be cleared with a scan tool or by performing the following procedure. (An engine remote starter can be used in place of a jumper wire for this procedure).
1. Turn ignition switch to the "ON" position.
2. Use a jump wire to ground DLC terminal "H" to "A" for 2 seconds.
3. Remove the jumper wire for aprox 1 second.
4. Repeat the grounding for 2 seconds.
5. An indication of success is when the Antilock" and "Brake" lamps turn on then turn off.

Functional Test (4WD)

Release parking brake and do not apply brake pedal.
Turn ignition switch "ON" but do not start engine.
Note Antilock lamp.
- Antilock and Brake lamps turn "ON" and go "OFF" after 2-3 seconds? Bulb check, OK. Check for soft DTC(s) stored.

- Antilock lamp turns "ON" for 2 second Bulb Check and then stays "ON"? See "Lamp ON" chart.

-Antilock lamp does not turn "ON" for a bulb check? See "Lamp Off" chart.

DTC(s) found. Refer to DTC chart.
No DTC(s) found.


TO BE CONTINUED, while I finish up the NO DTC(s) found part of "Functional Test (4WD)", start the test, conduct bulb check and scan for DTC(s)..
 

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Continued
No DTC(s) found.

Check Brake switch status with scan tool or jump *DLC terminals A&H.
"ON" idicates brake pedal applied- *DTC 15
"OFF" indicates brake pedal released- *DTC 14
*Note: Only seen when using flash codes by grounding DLC.

- Switch status stays constantly ON or OFF, refer to DTC 81 diagnostic chart.

- Switch status changes when pedal is applied.

Check 4WD switch status with scan tool-
Switch status change when lever is shifted from 2WD to 4WD?

Theres more, if we need to continue...
 

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Discussion Starter #4
Great. Thanks!

I'll look into this.
 

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Discussion Starter #5
I checked for the ABS codes.

The first time I checked I got 28 86 12 26 27 25 (I think that was the order).

Then I tried to clear the codes. Each time I would ground A to H it would make a groaning noise much like when the ABS activates and the noise was coming from the area of the ABS unit on the drivers side inner fender.

The codes never cleared after trying the 2-1-2 sequence several times. The ABS light stayed on.

I took it for a short test drive and everything was pretty much as before with the light on.

I returned home and rechecked the codes and got 12 25 26 27 28 86 - in that order.

I tried to clear the codes again and this time it worked on the first 2-1-2 sequence.

I took it for a test drive and the ABS light stayed off...until I was backing in my driveway and then it came back on. I turned the engine off and waited a few seconds and turned it back on and the ABS light stayed off. I tried pulling forward and then backing up again and it stayed off.

I did notice the parking brake went down pretty far last night when I pushed on it. I don't regularly use the parking brake.

I did do some brake work last summer but I never let the brake fluid reservoir get empty.

I also checked for engine codes and got a 36.:banghead:
 

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Sounds electrical.
 

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*12- Normal System- 2WD Brake Pedal Release I thought you had K2500 (4WD)? If so, could be an ABS phantom code...

25- Left Front Wheel Speed Sensor or Circuit open (static)
26- Missing Front Left Wheel Speed Sensor (dynamic)
27- Erratic Front Left Wheel Speed Sensor (dynamic)
28- no DTC description avail
86- Shorted Antilock Indicator Lamp..


My best guess, something amiss with the front left wheel speed sensor..

DTC 36- Check for fuel restrictions, lp health and fuel pressure @ IP inlet... One of them possible air scrambling PCM DTCs. Good Luck Hunting..
 

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Discussion Starter #8 (Edited)
I am assuming the 20's codes are input from each wheel that are tripping after the 86 code is set. The best I could find so far is that 86 is a short in the ABS indicator light.

OOOPPS too slow.

Thanks Heavy.

I did most of the work over the summer to the left front so maybe I knocked something loose or contaminated a sensor or something.

I saw the ServiceEngineSoon light flash a couple times over the last couple months so that is why I checked for those codes. I'll clear that one and see if it comes back.
 

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You can check the sensor by measuring the resistant at the sensor end of the connector.

It should not be 0 ohm and it varies as the wheel turns.

If it is 0, then the sensor is bad.
If it has resistant, then somewhere in the connections/cables are bad.
 

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Discussion Starter #10
The ABS light blinked a couple times here and there while I was driving. I checked the codes again and came up with only a 25, and 12 but I think that is 'normal. I'm going to check into it further when the weather is a little nicer.

For the code 36 on the engine, could that have been related to me working on the FFM and possibly getting some air in the system?
 

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The ABS light blinked a couple times here and there while I was driving. I checked the codes again and came up with only a 25, and 12 but I think that is 'normal. I'm going to check into it further when the weather is a little nicer.
12 is SOP (normal). 25 is left front WSS. I wished I had the option to wait for warmer weather.. Forced to go BOATing in the cold this past weekend.. hated it..

For the code 36 on the engine, could that have been related to me working on the FFM and possibly getting some air in the system?
Yes, air infiltration can generate a grocery list of DTCs, specially if you follow steps 3 and 4 of the factory procedure. Excessive cranking typicaly generates a grocery list of spooky DTCs. Thats why your supposed to CLEAR DTCs whenever your done "Bleeding Air From Fuel Supply System" and/or completed with ANY fuel system related maint and/or repairs... That last step is often skipped or ignored assuming the tech or DIY is even aware of it. Any left over DTC's may further complicate if not mislead near future diagnosis as you now have discovered..
Thats why I make it a practice to check for, make note of, and clear DTC's before as well as after any maint or repairs, just so I know if the DTC(s) were there beforehand or a result of whatever I just did..

Good Luck..




BTW.. I have found a way to thoroughly check aprox 95% of the 6.5's fuel supply system for potential air leaks in under 15 minutes.. Care to know how?
 

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Discussion Starter #12
That would be helpful.
 

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DS models, the IP fuel inlet supply hose is easily accessible and provides an excellent place to connect a hand vac pump w/ gage to pull a good 20"- 25" vacuum and observe the gage.
But first preparation which brings up a couple things to note before proceeding..

Tools needed: Hand op vac pump w/ gage and a few basic hand tools.
Tip: Having a valve stem and hand (bicycle) pump w/ psi gauge or fuel gage tapped into the end of the WIF drain hose will help in quickly finding any potential leaks that may of been discovered, see leaking below..

NOTE: Theres a couple o-rings used to seal the fuel sender and liftpump fuel line(s) connection(s). Depending on where you chose and to further expedite the test, plan on replacing both applicable o-rings (see FAQs for sizes) at the conclusion of the test to ensure an air tight seal/reassembly..

NOTE: If your fuel hoses, specifically the IP fuel inlet supply hose is old, hard, stiff, brittle, non pliable and/or already shows signs of cracking or sounds like a bowl of rice crispies when barely touched, plan on replacing it and all the others under the intake manifold to and from the FFM, return hoses, and WIF drain hose asap even if the test indicates its all good.. Like tires, rubber components such as fuel hoses, FFM o-rings, seals, etc should be inspected and replaced at least once if not twice a decade.. Fuel hoses are often one of those schelduled maint items thats always neglected until it either cost a couple needless PMD and/or IP replacements or starts to actually leak fuel. If it was only that easy all the time but the fact is many AIR LEAKS dont leak fuel or show any wet spots to indicate a leak is developing..
Air infiltration, fuel contamination and fuel restrictions is the 6.5s real kryptonite, not PMD goblins.. All im sayin' about that, lets proceed.



Quick Check
1. If easily accessible, disconnect and plug the fuel sender supply line feeding the lift pump. If not, move to the LP and cap off the fuel supply line feeding the FFM and IP there. The objective here is to quickly but temporarily cap or plug the fuel system supply line as far away from the IP as quickly possible to maximize "test coverage" area..

2. Disconnect the IP fuel inlet supply hoses, connect the vac pump, apply 20"-25" vacuum and observe the gage.

Vacuum should hold firm and indefinitely. If not, how quickly or slowly vacuum is lost indicates the size of the problem..
Try to do this test without draining all the fuel out of the lines, FFM, etc.. Keep it wet for the first test in case a leak is found.

If no leak is found, restore the fuel supply system, bleed air, and clear DTCs..







LEAKING
If you discover a leak, an easy way I found to FIND the leak is to pressurize the system while you still have the system capped or plugged off at the tank or LP. I used an old bicycle inner tube valve stem and my daughters bicycle air pump with gage.. Your local bicycle, tire, or tractor supply can likely hook you up with an old valvestem assembly or new tubeless valve stem for a few bucks that doesnt require cutting up an old/new inner tube.
Objective is to install valve stem into IP Inlet fuel supply hose and slowly pressurize the system to 15-20psi. If theres fuel still in the line, any potential air/fuel leaks will begin leaking fuel or hissing air or spitting air and fuel to help in the search. Fix as required, repeat until the system holds 20psi indefinitely... then repeat the vacuum test to quickly check your work..

The FFM and surrounding area are good breeding grounds and hang out for most annoying airheads...
Most rough smokey start ups not caused by faulty GPs or worn injectors are most likely caused by airheads developing and gathering in the FFM when parked for extended periods eg overnight, all weekend or weeks on end..
Its also possible for these airheads to sit and linger in the top of the FFM (air rises) until vehicle movement dislodges the air bubble or increased fuel demand sweeps them up and unannounced is forced to self purge. Self purge may cause several driveability symptoms as well as set numerous DTCs indicating faulty OS, CPS, PMD, and/or IP, cause the engine to fishbite or if more severe can cause an intermittent skip, buck and jump around violently (poor/rough idle quality), or if severe enough, can even cause the engine to just shut off as if a ghost turned the ignition off..

IMHO its this last "engine just quits" symptom thats nothing but a little known thus misidentified PCM ghost (PCM's Safety Chief) is routinely being mistaken for as just another passing PMD goblin... HTH GL
 

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Speaking of cold weather..


"Diesel fuels are more prone to water attraction and subsequent separation when subject to temperature swings. A fuel's composition and temperature affect the amount of water it can hold. Generally, the higher in aromatic content and the warmer the fuel, the more water it can hold in solution. That's usually not a problem until the fuel is cooled, causing the water to be released and settle at the bottom of a storage tank."


FTR. Our fuel tank is heated via fuel return system each time the vehicle is operated. How much of a temp change depends on how long the vehicle is operated. Thats why its a good practice with engine at operating temp, to drain the WIF drain valve more frequently during the winter months even if your using treatments and/or additives..​
 
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