Disco 2 @sierrafery

Good morning,

First, I would like to introduce myself – my name is Jacek.
I am the proud owner of a 2003 Land Rover Discovery 2, a lifted version. I have been driving the car for four years.
Last year, I decided that I wanted it to be eternal, indestructible, and resistant to everything.
Therefore, I made the decision to separate the frame from the body and professionally preserve the frame in the best possible way. I found a contractor who agreed to take on the task for a reasonable price (in my opinion). He performed the job, disassembled, preserved, and reassembled everything. Everything would have been perfect if not for the fact that the ACE system stopped working correctly.

Here, I am reaching out for help and support.

Before the repair, the system was functioning flawlessly. The system is sealed, the pump is replaced, the filters have been changed, but unfortunately, the symptoms are such that the car behaves correctly when turning left, but when turning right, alarms go off, and the red warning light comes on. We have already replaced everything – a new block (used, but tested), a new computer (used, but tested), new valves, and we also replaced the level sensors and accelerometers. Despite replacing the parts, it didn’t help.
The system still doesn't work.
I am looking for support because I am close to abandoning this system and installing a manual one, but considering the huge amount of work the mechanic put in and the time spent, I would still prefer to get the ACE system working again.

Does anyone have an electrical diagram of the ACE system or any idea what might be the cause that it works fine when turning one way but not the other?

After swapping the cables/connectors on the directional valves, the situation is reversed: the error occurs when turning left, but it works fine when turning right.
It is probably the wiring, but we have no idea where to find it. I need support.

Best regards,
Jacek

Jacek discovery 2 said:

After swapping the cables/connectors on the directional valves, the situation is reversed: the error occurs when turning left, but it works fine when turning right.
It is probably the wiring, but we have no idea where to find it. I need support.

Click to expand...

Hi. Yes, seems like a wiring issue on the DCV's circuit but to confirm that you need a compatible diagnostic tool cos that "parts darts" game you played by replacing parts randomly is ineffective.. if you know how to work based on the diagrams you have them all HERE and the connector views HERE so check continuity to the DCVs from the orange plug near the engine bay fusebox/C0377 pins 8 and 14 to the same colour wires at the block if you see what i mean. Good luck

sierrafery said:

Hi. Yes, seems like a wiring issue on the DCV's circuit but to confirm that you need a compatible diagnostic tool cos that "parts darts" game you played by replacing parts randomly is ineffective.. if you know how to work based on the diagrams you have them all HERE and the connector views HERE so check continuity to the DCVs from the orange plug near the engine bay fusebox/C0377 pins 8 and 14 to the same colour wires at the block if you see what i mean. Good luck

Click to expand...

Thank you very much! I am an intermediary between the forum and my mechanic, and I will pass your suggestions to him. We’ll see how it goes. Best regards, Jacek.

Jacek discovery 2 said:

Thank you very much! I am an intermediary between the forum and my mechanic, and I will pass your suggestions to him. We’ll see how it goes. Best regards, Jacek.

Click to expand...

"During the attempt to test the DCV1 and DCV2 valves using a scanner, a problem occurs when trying to check DCV1. Specifically, the vehicle tilts to the right and stays in that position until the warning light is triggered and the main relay is turned off. After turning off the ignition and turning it back on, the system is ready again. During driving, when trying to turn right, a red warning light turns on. When measuring the voltage on the DCV1 and DCV2 valves with a multimeter during the test, the multimeter shows that DCV1 has a constant voltage of 3.2V, which holds until the error light comes on. However, during the DCV2 test, the multimeter shows the voltage rising from 0 to 5V and then decreasing from 5V to 0V, during which time the vehicle tilts to the left and returns, cyclically (click, click). By swapping the connectors, a mirror image effect occurs, meaning the fault follows the connector. In conclusion, the ECU is incorrectly controlling DCV1, supplying a constant 3.2V instead of a variable 0-5V

The entire new installation from the blog is directly connected to the ECU to bypass the original installation and the orange connector.

Jacek discovery 2 said:

the multimeter shows that DCV1 has a constant voltage of 3.2V,....

Click to expand...

Jacek discovery 2 said:

The entire new installation from the blog is directly connected to the ECU to bypass the original installation and the orange connector.

Click to expand...

If it was not made some mistake with that bypass and the wiring is intact the only problem can be the ECU in this case

sierrafery said:

If it was not made some mistake with that bypass and the wiring is intact the only problem can be the ECU in this case

Click to expand...

No mistake was made (on this section) and the cause is not the ECU. Measurements with a multimeter directly on the output pins from the ECU show the same values. This means that the control of the DCV1 valve is already incorrect at the output of the ECU. The problem lies with something responsible for providing the valve with a modulated 0-5V voltage, instead of the constant 3.2V in this case. There is something responsible for modulating the voltage, something that instructs the ECU to convert the supplied voltage into a modulated voltage, and when turning right, something causes the voltage not to be modulated, but to provide a constant value, which consequently causes excessive pressure on the actuator and triggers a pressure valve error. However, the valve itself is not the cause, but the effect. The cables, aside from the replacement, have been checked for continuity. All the cables that meet in the orange connector have been checked. All other cables related to the ACE are part of a different wiring harness (under the cockpit).

The problem is probably not with the cables themselves, but with something that specifically determines the voltage that should be applied to the valve. Something is preventing the control of the valve, there seems to be a conflict between factors. The ECU receives an incorrect signal and passes the same error to the valve.

The problem is not at the output of the ECU but at the input to it. We have replaced the ECU, but the problem remains.

"11 is the engine control unit, and 11? SLABS?"

"Can it interfere with the ECU's operation?"

Jacek discovery 2 said:

"11 is the engine control unit, and 11? SLABS?"

"Can it interfere with the ECU's operation?"

Click to expand...

The ECM or SLABS would not affect how the DCVs are managed cos it's about vehicle speed and rpm inputs necessary for the overall ACE activity, none of these inputs would cause that constant voltage on only one DCV as both should have 0V with stationary vehicle, the DCVs have common 5V positive feed and the voltage is modulated on the earth paths(PWM) with 200Hz signal and the only part which can affect the DCV's management could be the accelerometers

Jacek discovery 2 said:

No mistake was made (on this section) and the cause is not the ECU.

Click to expand...

Jacek discovery 2 said:

There is something responsible for modulating the voltage, something that instructs the ECU to convert the supplied voltage into a modulated voltage, and when turning right, something causes the voltage not to be modulated, but to provide a constant value, which consequently causes excessive pressure on the actuator and triggers a pressure valve error.

Click to expand...

If you know that for sure why did you ask? the DCV is not a pressure valve, it's flow controll solenoid ... also IF there is a resistive short somewhere which doesnt react to the multimeter it could have ruined the replacement ECU too as a circuit reacts differently to 0-5V PWM than to 3V DC applied by the multimeter on resistance check ... you keep talking about voltages but did you measure the circuit's resistance across the common DCV feed wire and the problematic DCVs earth path even if it can be irrelevant?

though as i said this issue needs a compatible diagnostic tool(hawkeye is the best with ACE) cos you can't check correct inputs/outputs or an accelerometer with multimeter(eventually with an oscilloscope) and if everything is OK (wiring ECU, valve block) theoretically this symptom can be caused by a miscalibrated or faulty accelerometer, read the attachment maybe it becomes clearer