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Thread: Error code 78 pressure accumulater sensor

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    Error code 78 pressure accumulater sensor

    Flashing skidding car, ASC and then ABS light comes on after 50kmh. DTS 78 so I'm assuming it's the ABS system. Relays in engine compartment seem fine, though not quite sure what the one with the heatsink is actually.
    Has anybody seen this before?

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    To confirm, you've performed the flashy dash diagnostics, and all 3 lights (skiddy car, ASC and ABS) all flash out 78 as a code?

    Don't trust any other diagnostic method than flashy dash on these cars.

    If it is only 78, the service manual does indicate either a wiring issue with the pressure sensor in the ABS pump's accumulator, or an actual leak/fault which is causing it to lose pressure.

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    Thank you for the reply. Yes using diagnostic connector without a 1 and 4 linked. The fluid level is unchanged and I tested resistance levels across the 3 ABS connectors all where text book values. The only component i couldn't check was the relay with heat sink next to the normal ABS relay.
    I also applied 12v to pins 23 and 24 of the pump and verified it's operation, not the sound I was expecting though, did sound a bit clunky.

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    Have a look at your brake ABS block under the bonnet at the windscreen on the passenger side.
    If it has a round sphere a bit bigger than a tennis ball then it may be faulty. There was a recall on cars with this sphere as it was a pressurised gas that was in the sphere, but the system deteriorated over time and the gas got into the brake fluid causing it to loose hydraulic pressure and giving a spongy pedal and potential brake failure of very bad performance.

    Only saying this due to the words pressure accumulator, I could be way off, but it's worth having a look, cheers Louis
    Updating Soon!! 1998 Legnum VR4, fully serviced every 4500 miles. Fully Amsoil'd. Falken 453's, EVO 8 FQ320 rear diff.

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    Thanks Louis. The part number is MR407436. It has what I believe is has the abs pump motor but no sphere or accumulator like our ayc pumps.
    Screenshot_2022-09-02-08-52-37-495_com.ebay.mobile.jpg

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    Quote Originally Posted by babasvr4 View Post
    Thanks Louis. The part number is MR407436. It has what I believe is has the abs pump motor but no sphere or accumulator like our ayc pumps.
    Screenshot_2022-09-02-08-52-37-495_com.ebay.mobile.jpg
    I know this isn't your photo, but it's things like this that really irritate me.

    There are connectors no more than 6 inches away from the ABS unit for every single one of those wires which have been cut. Rather than being a simple plug-in replacement part, whoever "removed" this (and, given the photo, is/was presumably trying to sell it) has added at least 30-60 minutes time to the installation, and introduced the potential for future issues at these joints that will now need to be made, because they couldn't be bothered to spend 30 seconds disconnecting the electrical connectors.

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    I know exactly what you're saying, I unplugged all 3 in seconds and measured the modulator side easily. It's sloppy work, all but useless really.

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    Just in passing, if you have evoscan and a cable you can activate the abs on each wheel individually and hear art working. (it helped me track down an issue in the past)

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    Ok, I didn't realise that side of evoscan actually worked. It's a PFL so hopefully it works. I think I've tried it way back but I'll give it another go!
    I have looked around for another unit but nothing available in Australia so far.
    Cheers.

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    No luck with evoscan, possibly the wrong cable for those functions. It comes up with arithmetic overflow trying to connect to that side of the ecu.
    The only thing I haven't sorted is the Omron relay with heat sink for the ASC. I don't have a diagram for it and and the only reading I get is something like 3.6 M ohms.

    Whether it's in or not makes no difference. Hopefully someone knows of an alternative relay as it's difficult to track down a replacement.
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    I feel this is worth sharing as I may have tracked down the specific fault, ABS modulator (pump) fault throwing out the ASC. Section 35C-47 shows the resistance readings of the ASC solenoid valves, expected and actual. Managed to find a second hand unit so will verify once it turns up. Car is ok to drive other than no ABS and those bloody flashing lights.
    IMG_20220907_090028.jpg

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    Unfortunately the Mitsubishi specs are incorrect, picked up a second abs pump for testing and it reads the exact same values as mine. Unfortunately error 78 is only pointing to what is not working and not the real issue.

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    According to the Japanese manual, the resistances are different to the European manual, and match closer with what you're measuring:

    asc-jpn.JPG

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    Thanks for the confirmation. While it's great to see the abs is fine it's back to the drawing board looking for faults.

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    ABS pump assemblies did give exact same reading but temp plugged in the replacement, all errors disappeared. Installed the unit and all good now. I can only assume that either the DC motor is going or the pump side is worn. Changeover was easy enough, bleeding the lines, wheels off and on etc took longer.

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    Good work on clearing the codes

    Happy to hear the new pump assembly did the job, though a shame the diagnostics weren't quite as clear-cut as hoped!

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