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Code P0778 help to diagnose

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Old 07-19-2022, 05:30 PM
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Default Code P0778 help to diagnose

Hi Jag fam,

looking to get some instructions on how to diagnose my p0778 code. 2/4 brake duty solenoid.

I have a 2004 Jaguar x type and it was 05/04mfd.

Can anyone help with what I can do to try to diagnose the problem?

Any help is appreciated!

Thanks
 
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Old 07-19-2022, 06:00 PM
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Old 07-19-2022, 07:24 PM
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Jason, what you want to do is first put the multimeter on the 2K resistance scale and then touch the leads together. You should see the meter read out something like 0.3 (ohms). Note the value that you get. Any which way, it should be under 3 ohms.

Now, for proving what may or is not the problem, start with measuring between pins 16 and 18 at the tranny plug for the solenoids. You should something around 2.9 ohms (2.7 to 3.1ohms). Remember to subtract out your lead resistance (the number i told you to note). Next, do a resistance check between Pin 16 and the metal body of the tranny. You should get more than 2K (normally indicated by "OL" being displayed).. The final check is to measure between pin 16 and Pins 9, 10,11, 12, 13 14 15 and 17 (one at a time). You should get a reading in the upper single digits and the lower teens (6 to 18 ohms).

If the measurement between pins 16 and 18 showed a high resistance, you have a problem with the wiring to the solenoid or the solenoid is toast. I would recommend replacing the solenoid (may be a good idea to change out all the soienoids, not that hard to do and also not too expensive as I recall) The same is true if you got an extremely low resistance (under 2 ohms).

Next, when you measured Pin 16 to the tranny body, if you saw any resistance, change the solenoid.

Finally, when you measured between Pin 16 and the other pins, if any of those showed a resistance of less than 3 ohms, then you have damaged wiring and you should replace your solenoids (the whole set).

If all the resistances were reading good, then your problem is elsewhere, let me know and we can take things from there.
 
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Old 07-20-2022, 01:20 PM
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Default Multimeter help for p0778

Thermo, Dell and Anyone else

I have a multimeter but when you say to put it on 2k resistance scale I’m not sure which one to use to test the pins.

Can someone be more specific as I am not as electronically inclined.

Specifically, what setting do I use for 2k as mentioned by Thermo and what side does the red one go into? I’m not multimeter inclined


What one does the red go into and what setting to test for the 2k? Thanks
 
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Old 07-20-2022, 04:16 PM
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Jason, turn the dial of your multimeter so the 2000 tab in the dark green section with the funny looking "O" (like it has feet, that is really the sign for ohm, or resistance). As for the red lead, that will go in the right terminal at the bottom that has the matching ohm symbol.
 
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Old 07-20-2022, 05:17 PM
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Old 07-21-2022, 03:29 PM
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Okay,
Am I to have the battery connected or disconnected during these tests?

I had it disconnected and here is the
update on the pins:

I had the meter on ohms 2000 like thermo said,

P1)
checked the jb155 pin 18 to ground and got under 5ohms.
(I got 017 @2000 scale)
Does this mean under 5 OHMS? If so how many?


Then I did
P2
(I got reading 033 @2000 scale)

Now, I’m unsure as to what pin is what on jb131

Can anyone help identify?
Pictures attached



Help with PIN number on jb131 in picture
 

Last edited by Jason Holman; 07-21-2022 at 03:59 PM.
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Old 07-21-2022, 05:02 PM
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Jason, when doing resistance checks, you always want to have power removed. With that being said, simply having the car off is good enough in most cases.

As for your reading of "017". From what I can tell about your multimeter, on the 2000 scale, you do not have a decimal point. So, you would be seeing 17 ohms. Since you have a 200 ohm scale, you can use that too which may be advantageous for the checks that you are doing.

As for pin 3 of the plug you are showing, rotate the plug so the hoop for the lock assembly is on top (rotating 135 degrees counter-clockwise based on the picture you show). Now, look at the top row. The middle pin is #3.
 
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Old 07-21-2022, 05:10 PM
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Thermo,

I see where pin 3 is now with your description.

In the steps, it asked for pin 17, if I can’t read the numbers so you know which pin that is on jb131 in the picture also?

I looked for a diagram but can only find the one for jb155 only.

Any help on that?
 
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Old 07-21-2022, 06:12 PM
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Electrical guide attached
 
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