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jm1489

Member Since: 09 Dec 2019
Location: Lincolnshire
Posts: 42

2002 Range Rover Vogue 4.4 V8 Zambezi Silver

Solenoid c malfunction code P0760

L322 V8 4.4 petrol 5zf trnasmission. Swapped out solenoid c with a tested part from RRPhil, still have the "trans failsafe" and limp with code, any ideas.... wiring loom? Any help would be appreciated.

28th Jan 2020 12:26pm

RRPhil

Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 960

P0760 is a rationality fault (as opposed to an open or closed circuit) so tracing it can be tricky. You could certainly check the integrity of the internal wiring loom by measuring the resistance between pins 4 & 16 at the 16-pin connector

Click image to enlarge

or, better still, check the wiring all the way from the ECU to the solenoid by measuring the resistance between pins 16 & 21 at the 40-pin connector

Click image to enlarge

You should measure a resistance of around 26-28Ω at ambient temperature.

However, if the problem is (say) temperature related or intermittent then you’d be fortunate if this ‘static’ test happened to reveal it.

Phil

28th Jan 2020 4:56pm

jm1489

Member Since: 09 Dec 2019
Location: Lincolnshire
Posts: 42

Ta Phil, the old chestnut.. finding a fault when its not a fault! Gut feeling is the harness, again, as with other stuff on this RR, someone has been there before me, a couple of the solenoid pin clips had been broken? Either someone has been really ham fisted or they have become brittle and broken with vibration, no signs of fragments in the pan.

28th Jan 2020 8:41pm

RRPhil

Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 960

The solenoid connectors do get very brittle with age/fluid temperature

Click image to enlarge

The colour of them gives a clear indication of how hot the transmission has been running. The oil breathers shown below are made of a very similar plastic to the connectors and you can see how the fluid temperature has affected their colour

Click image to enlarge

I’m away now until after the weekend, but if you want me to send you a different harness to try, just shout

Click image to enlarge

Phil

29th Jan 2020 1:05am

jm1489

Member Since: 09 Dec 2019
Location: Lincolnshire
Posts: 42

On the to do list, when weather improves I will chuck some time at the RR, my T5 is getting a bit of tlc at the moment.. long overdue. I will get RR into limp mode before check resistance at the ecu.

16th Feb 2020 12:22pm

jm1489

Member Since: 09 Dec 2019
Location: Lincolnshire
Posts: 42

I think I have been a numpty! Just had a look on a BMW site and saw same post from you regarding the solenoids.... I think the open gearbox picture was back to front and in the process of visualising it lying on my back I realised that I probably changed the wrong solenoid! I think I changed solenoid A? I carried out an ohms check at the ecu and got a reading of 26. Would a faulty solenoid show a different reading or is purely to check the wiring resistance?

2nd Mar 2020 10:05am

RRPhil

Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 960

The resistance check purely shows that the solenoid’s windings, and the associated wiring and connectors, are intact and doesn’t tell you if the plate, which clicks backwards and forwards inside, is moving freely/correctly. At the centre of this plate is a ball which acts as the valve which seals off the oil feed passages. This internal mechanism is extremely simple and it’s hard to imagine much that could go wrong with it.

Click image to enlarge

When the solenoid is activated (with 12v at >0.22A) its armature attracts the plate, against the return spring, and the ball blocks the ‘exhaust’ drilling up the centre of the armature. At the same time, it allows fluid pressure to flow between the regulated 5 bar feed and the shift valve, thereby moving the shift valve.

When the current is switched off (<0.08A) the return spring forces the plate away from the armature and the ball seals off the feed port, and at the same time allows the fluid pressurising the shift valve to exhaust to tank up the centre drilling in the armature.

The transmission controller which is detecting a fault can only sense if there’s an electrical issue and not whether there is a mechanical/hydraulic fault. It bases this on the voltage measurement at the solenoid, i.e.

P0760 ‘rationality’ error – when the solenoid is under current the solenoid voltage is between 1.0V and 1.44V or when it isn’t under current it’s between 0.85V and 1.44V

P0761 ‘disconnection’ error – when the solenoid is not under current the solenoid voltage is between 0.35V and 0.85V

P0762 ‘ground short’ error – when the solenoid is not under current the solenoid voltage is between 0V and 0.35V

P0763 ‘power short’ error – when the solenoid is under current the solenoid voltage is between 1.44V and 5.0V

The three MV solenoids are identical so you could swap them around to see if the issue moves with the solenoid.

Click image to enlarge

Phil

2nd Mar 2020 1:53pm

jm1489

Member Since: 09 Dec 2019
Location: Lincolnshire
Posts: 42

Hi Phil, eventually got around to swapping the solenoid out, thank you Corona 19 thingy for giving me the time. A few miles under the belt and everything seems to be working as god had intended, nice car to drive once again. Thank you for your help. I would have fixed this first time around if I hadn't been such a numpty but at least I am getting to know the ins and outs of my L322.

27th Mar 2020 1:14pm

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