Disco 2 ACE light - engine speed missing

Morning all, driving to Ipswich this morning and noticed the ACE light (amber) had come on, no audible warning I just happened to notice it. Stopped and started the engine and the warning light never came back on.
Plugged in the Nanocom just now and the only fault (anywhere) was in the ACE section "13-03 Engine Speed Signal Missing". Cleared it and it's stayed cleared.
I've had no fluid loss and there are no other fault codes, so question is would the no engine speed fault put the light up, and if not what could it be as it hasn't come back?
Also no fault codes on Lynx and the system pressure at idle is fluctuating between 1.47 and 4.77 bar with odd spikes to 14 bar
cheers

I did a system test on Lynx and the test failed on the following:

Direction Valve 1: 80ms OFF time (should be 15-60ms)

All the others were within range. I have no idea what that means! Whether it's related to old or leaky ACE rams, or a pump fault

Does anyone know if the direction control valve can be purchased as a separate part? I have found reference to it in RAVE, but it doesn't mention direction control valve 1 / direction control valve 2.

Whole block, but you MAY be able to get hold of seals.

But first change the fluid, and check the pump

MJI said:

Whole block, but you MAY be able to get hold of seals.

But first change the fluid, and check the pump

Click to expand...

Thanks, I wondered if it was available separately as there is a section in RAVE describing removal/replacement.

I haven't driven it again since, but after stopping the engine at home and then driving to work the light never came back on. I might do the system test again and see if the results are different. I do have a weeping front ACE ram and the rear one looks quite old too. if they are easy to change I might just change them and see how it goes. I can't imagine the whole block is particularly cheap.

tom1979 said:

Does anyone know if the direction control valve can be purchased as a separate part?

Click to expand...

I've just seen this post cos i missed it first time, if it's about a DCV you can buy as spare but they rarely fail and if they do you get open or short circuit fault code on it.

tom1979 said:

the system pressure at idle is fluctuating between 1.47 and 4.77 bar with odd spikes to 14 bar

Click to expand...

this can be due to air in the system, failing pump or faulty pressure transducer, here is a list with correct live data at idle with vehicle stationary on even ground:

1. DCVs (both) - .001A
2. Pressure control valve: 0 - .012A
3. Pressure sensor: varies between 16 and 19 but if it's out of that range the transducer is gone
4. Residual pressure: between 3 - 6 Bar but can be higher after the vehicle was driven or the ambient temp is low
5. System pressure: around 6 Bar fluctuating max. 20%
6. Accelerometers: 0.01 both

for troubleshooting purpose: the resistance of both DCVs(top of the valve block, DCV1-toward front; DCV2-toward rear)= 2.7 Ohm, pressure control solenoid(on the left side of block) = 5.7 Ohm.

sierrafery said:

I've just seen this post cos i missed it first time, if it's about a DCV you can buy as spare but they rarely fail and if they do you get open or short circuit fault code on it.

this can be due to air in the system, failing pump or faulty pressure transducer, here is a list with correct live data at idle with vehicle stationary on even ground:

1. DCVs (both) - .001A
2. Pressure control valve: 0 - .012A
3. Pressure sensor: varies between 16 and 19 but if it's out of that range the transducer is gone
4. Residual pressure: between 3 - 6 Bar but can be higher after the vehicle was driven or the ambient temp is low
5. System pressure: around 6 Bar fluctuating max. 20%
6. Accelerometers: 0.01 both

for troubleshooting purpose: the resistance of both DCVs(top of the valve block, DCV1-toward front; DCV2-toward rear)= 2.7 Ohm, pressure control solenoid(on the left side of block) = 5.7 Ohm.

Click to expand...

Many thanks. Would you suggest replacing the actuators first to rule out any pressure drops in leaks? The rear doesn't leak, and the front is only wet, there is no noticeable fluid loss

There should not be a pressure drop due to such small leak, was the filter changed/cleaned since you own it?... if not fix that leak, replace or clean the filter and bleed it well, can you see serious activity of the fluid in the tank with engine running?

I have a filter, but I haven't done it yet as I was waiting until i'd got some decent good-fitting allen keys! The reservoir is pretty "active" when the engine is running.

The light came on after driving down a fairly bumpy road, but hasn't come back on since.

I will compare the readings on the Lynx with yours above and see if there are any differences.

Many thanks,

sierrafery said:

There should not be a pressure drop due to such small leak, was the filter changed/cleaned since you own it?... if not fix that leak, replace or clean the filter and bleed it well, can you see serious activity of the fluid in the tank with engine running?

Click to expand...

Thanks for giving the normal sensor readouts. I have re-run the system test where the ACE system is activated and monitored and this time it passed. I have put below the readings at idle, which do vary slightly from yours. I don’t know whether this is anything to be concerned about or not. The system pressure does vary considerably, and tends to be on the low side.

The only fault code that was originally present was “engine speed missing” and not related to pressures or open-circuits so hopefully it was just a glitch and suggests more an electrical problem than a mechanical failure.

I have also put a video on YouTube of the live data whilst the engine was idling so that you can see how much variation there is in each reading – hopefully they are fairly normal ?! This was all done using Lynx as I have read that Nanocom can be hit and miss with the ACE system.

- Direction Control Valve 1 : 0.01A
- Direction Control Valve 2 : 0.01A
- Pressure Control Valve : 0.09 A
- Pressure Sensor : 16.65 bar
- Residual Pressure : 5.07 bar
- System Pressure : 14.89 bar
- Upper Lateral Acc : -0.03 G
- Lower Lateral Acc : 0 G

All of the above varies as per the video.

Video:

IMO you need a new pressure transducer as everythig to be perfect

I ordered a new pressure transducer, but it hasn't come yet! Has anyone any tips for removing it without potentially damaging the overly delicate pipes that surround it?

27mm deep drive socket

As to pipes I just pulled mine down slightly to give more room.

MJI said:

….As to pipes I just pulled mine down slightly to give more room.

Click to expand...

Really I thought they were too delicate to even look at without causing a leak!

tom1979 said:

Really I thought they were too delicate to even look at without causing a leak!

Click to expand...

I pulled mine around a lot as they are quite large diameter. Especially the pump hoses.

I shoved the socket on an extension through and unscrewed. Pump are 3/8 BSP Ram are 1/4 BSP. ram is pretty flexible

All done, new transducer and new filter. Readings are the same! Fluctuates quite a lot after staring the engine which you’d expect but then settles to around 6 bar and starts fluctuating down to 2 bar and back

I forgot, did you change the filter too? if not do it

sierrafery said:

I forgot, did you change the filter too? if not do it

Click to expand...

Yes I did the transducer first and then the filter. I wonder if it’s the weeping ace ram at the front or if there is a pressure relief valve somewhere.

We’re going away in it this weekend so hopefully it will be ok!!

Did you bleed it after the filer change?

sierrafery said:

Did you bleed it after the filer change?

Click to expand...

No? I never have done before either