Technical P176862 - Hydraulic Circuit Accumulator discharged signal compare failure

[jchi7613]

Hi, I have a 2017 Fiat 500 with an intermittent check transmission light which results in the car going into limp mode, only gears 1-3, R work. I turn the engine off/on, and car runs fine.

Recently had a diagnostic at Fiat and test returned code P176862- Hydraulic Circuit Accumulator discharged - signal compare failure.

Fiat are telling me I need a new valve unit/cable harness/actuator for $3000+, I find it hard to believe it needs a new unit as the car runs fine when not in limp mode.
Anyone had this issue before? suggestions appreciated.

Thanks

 

[varesecrazy]

Hi

Im not sure how much this system has evolved in the last 15years..

But member @irc has experience of the older units and may be able to answer this

Charlie

 

[irc]

On an old 169 Panda, after being 100% sure that there are no wiring problems, (and providing it has never leaked any Selespeed fluid) I would probably change out the accumulator, and then possibly the pump motor if the problem remained. Because a failed accumulator will rob the system of some Selespeed fluid, it will then need a small top-up (Tutela CS-Speed).
Not sure how different the new ones are, but these operations are totally DIY-possible on the older ones, as long as you can de-pressurise the system first.

Dealers (at least UK ones) won't do this, as they tend to treat the actuator as a single unit.

However, if it has ever leaked fluid then all bets are off!

 

[varesecrazy]

Thanks IRC


Looking at the OPs image

The scan show 39 failures.. if no fluid has been added.. that seems a little odd


Why is the accumulator 'flat : low on pressure'?

 

[irc]

Thanks IRC


Looking at the OPs image

The scan show 39 failures.. if no fluid has been added.. that seems a little odd


Why is the accumulator 'flat : low on pressure'?

Hard to say from a distance, but a signal miscompare *could* be from the pump creating pressure which is fluctuating because the membrane in the accumulator has failed.
Or it could be a failed pressure sensor.
Or a wiring problem.

Of these, a wiring problem could be the cheapest if it can be repaired without a new harness.
Assuming the parts are the same on later actuators, an accumulator is about £100 in the UK, and is basically a consumable part, and the pump motor is used on a number of cars, from Alfa Romeo to Ferrari, with prices varying widely.

A pressure sensor failure would be unusual, and could be a simple fix if it is externally accessible, and the component is available (or can be scavenged from a failed unit/scrapped car)

(Parts availability is pretty dire for the units used on the 169 Panda/Grande Punto/early 1.2 500s, especially seals, so I have mostly stopped working on Dualogics at the moment - I have 3 units waiting for repair under my workbench which haven't moved in 6 months or more.)