Nanocom Codes and Diagnosis - 3 Amigoes
Since I first posted up the 3 Amigoes Symptoms and Remedies post (August 2011), I realised that the posting, whilst helpful, was pretty naive. Since then, taking a more Nanocom diagnostic approach, I've put together a list of what errors can be thrown up and where to look for them, including some of the reasons why things go bing, bing, bing.... look the 3 amigos are here.
To head off criticism, yes some of these may have been in the good oil forever, but I can't recall seeing a list of Nanocom errors (ok, only 2) and what areas to consider. As usual, if I'm not 100% correct, I know people will provide the necessary feedback.
BTW: You can also work this list from back to front. Rather than starting with the nanocom error, look to see what was happening or the last thing you changed. New brake pads and now the three amigos - upsetting the signal at the wheel sensor = wheel sensor fault.
An SVS fault error could be:
- an SVS fault. This is causing by leaking seals, allowing brake fluid to go onto the contacts. Check the resistance between pins 6 (black wire if back probing) and 9 (red wire if back probing). Pins 6 and 9 are the outer pins on each side in the middle row. Around 3k ohms is the value given by the shuttle valves contactor when no pressure is applied on the brake pedal. Resistance varies depending on how much pressure is applied to the pedal. More pressure will drop it to 2k ohms, more again to 1k ohms. If reading other than 3k ohms when no pressure, chances are you have a shuttle valve contactor problem and the switch will need replacement.,
- A loose wire on the ABS block. If the three amigos come on when you are on a smooth road, then it could be as simple as this. Push all of the wires back into the ABS electrical connector in the engine bay, especially the yellow green wire. Another fix is an Option B mod – this bypasses the ABS connector and the loose wire….
- Faulty earth. Fix the earth or spend lots of time performing an Option B mod. This provides another earth….
- Broken pcb lands or connectors. Option B is specifically to fix this problem, which is a known weak design point in the ABS modulator. Or you can replace the ABS modulator (major cost). Look up Option B on aulro.com or google it. Lots out there about it.
A bit of tongue in cheek here, but an Option B mod could be a long fix for a simple problem. Yes, the problem will go away, but it could have been fixed a lot easier.
Sensor failure error could be:
- Grease / dirt / mud is causing a problem with the sensor getting a reading – maybe short circuiting the sensor, not allowing a clean signal to be provided. The sensor itself is in the hub, so mud can’t get affect it or the choppers as easy as a road oriented car.
- Faulty sensor - Each wheel speed sensor has a resistance of 950-1100 ohms.
- Crook bearings, causing the sensor to not get a reading all the time, hence error. Check for excessive play in the hub etc.
- Brake pads - A worn brake pad or non-Land Rover Brake pads can set up a resonance vibration in the wheel hub. This vibration can interfere with the ABS sensor signal. When the ABS sensor signal is interrupted an ABS wheel speed sensor fault can be logged.
- Broken wire between the sensor and SLABS – highly likely if you are off road or have just been offroad.
- high resistance connector – there’s a connector between the sensor and the computer; mud and / or water can get into it, even though its got a pretty good seal.
- Faulty channel in SLABS – the electronics in the SLABS that receives the signal can fail. Replace the SLABS. (pretty rare to date, but may become more common due to the age of the component). Also, it may be as simple as a solder joint in the SLABS going open circuit, which may make it repairable, rather than an integrated circuit etc).
BTW: you can test for wheel sensor operation / issues without a Nanocom. (Thanks to Danny_bristol for this). This is because the SLABS ECU is constantly comparing the overall calculated vehicle speed to each individually measured wheel speed and apparently provides a speed signal to the speedometer as well. Jack each wheel in turn off the ground and start the engine. Engage a gear (manual) or put the auto into Drive. The wheel will turn giving a speed reading. If it doesn’t then there is something wrong with that input into the SLABS. If no obvious wire issues etc, try changing the sensor from one side to the other, to see if that’s causing the problem.
Lastly, another good site about Disco II ABS Data is http://www.rswsolutions.com. Talks about how the ABS, HDC and TC works on the D2, as well as detail on SVS and wheel speed sensors.
Depends - Auto or Manual? TD5 or v8?
Quote:
Originally Posted by
biggin
As an alternative to jacking up each side to check the sensors via speedo, could you not just have one of the four sensors connected at a time and go for a short drive?
Just trying to think of a way to test them for those of us with auto diff unlockers.
From looking at the workshop manual, it appears that the vehicle speed signal comes from the SLABS ECU, as provided by the wheel sensors, which is why lifting one wheel at a time works to isolate a sensor fault.
In autos, a second signal is derived from the main gearbox output shaft speed, and is sent by the Electronic Automatic Transmission (EAT) ECU though the Controller Area Network (CAN).
These signals are used by the engine control module (ECM), cruise control and speedometer.
So, if the car is a manual and a TD5, you can most probably drive the car to isolate a sensor issue.
For manuals and a v8 it appears that the car won't run properly, as the ECM hasn't got any values as input and will most probably register a rough road condition. HDC / ABS warning light will come on - which you won't see, as they are already illuminated.
For auto TD5s, driving a car won't work, due to the speed signal coming from the auto.
