Thread: 3 Amigos driving me iNsAnE!!!

Hi Folks, 2001 TD4. I've been trying to sort the 3 Amigos for over a year now. I'll preface this by saying that I am very competent with electronics and electromechanics.....

So, I've changed the brake switches, fixed the HDC switch wires, changed all 4 wheel speed sensors for new ones, Checked the hubs, checked the reluctor wheels, checked all wiring, checked all fuses & relays, checked the G sensor and measured all signals to the ABS modulator. All present and accounted for although the two rear wheel sensors read 1200 ohms Slightly high). Can still happily pick up a signal on the multimeter (AC volts and frequency) when the wheel is spun though.

Then I pulled the ECU off the pump to check for dry joints and shorted/ open circuit solenoid coils. All appears fine. But the 3 amigos remain steadfastly on.

So I'm leaning towards a faulty ABS pump. I can get another locally for $330 with warranty but wanted to check on something first..... This one has the SRB000110 pump - not the older Wabco one that gets the shuttle valve fault. The RAVE manual notes that from 2002 a different "active" wheel speed sensor was used. But I'm wondering if the active sensors are supposed to go with this SRB000110 pump? Or did the SRB use both the old and new sensors? See, the fault was intermittent before I changed the sensors - now it's permanent which still makes me suspect the sensors even though they seem to measure OK.

It would help if there was a LR dealer nearby that I could access a Testbook to look at codes.

Any clues / suggestions?

Thanks - Pat

I've actually fixed it folks, although at considerable cost that probably could have been avoided.

I purchased a Hawkeye reader - these things are awesome and probably should be a must have for FL1 owners who like to tinker. It gets you into everything. You can even re-code new keys!

In this case the live data from the ABS ECU told me that there was an electrical fault from the left rear wheel speed sensor - essentially no signal. However the sensors had been replaced with new ones and measured fine with a multimeter back at the ABS computer connector. You could see the resistance across the terminals was the same as the others (the old sensors are just a coil) as well as see the pulses when you rotated the wheel on a scope - all looked the same. I even swapped left to right to no avail. Which led me to believe there was a fault with the input circuit in the ABS ECU so I set about cracking open the computer and looking for dry joints etc. Still no good so I ordered a second hand ABS pump and ECU ($350) expecting to swap the ECU and fix the fault. But of course no - the fault still existed upon swapping in the new ECU!!!!!

Then I was driving around with the Hawkeye connected and in live data mode displaying the wheel speed sensor output and I noticed that the LH rear was flickering on and off as we drove. Although I had previously ruled out a loom fault with the earlier tests this led me to believe I might have an intermittent connection in the loom & sensor lead, or a chafed wire shorting to chasis earth. I started by re-taking my measurements at the ABS connector but this time I also looked for shorts to earth on either of the wires to the sensor. And there it was. A dead short to ground on one pin!!!

So I next disconnected the sensor back at the wheel and the short disappeared leading me to conclude that there was a short to ground in the sensor itself. And so it was - a faulty new sensor that tested fine across it's output pins but had one side shorted to it's outer casing that then shorted to chasis ground when installed in the hub. A FAULTY BRAND NEW SENSOR!!! I'm waiting on another new one but in the meantime I have removed the brass sheath that they sit in and have covered the sensor in two layers of insulating heat-shrink and all is working properly again.

I can only guess that it did actually originally have a faulty wheel speed sensor, and that was swapped out with the "new" set that appeared to test fine but was ultimately still faulty. Total cost - about $450 for the Hawkeye, $45 for the sensors, $350 for the ABS pump and ECU that ultimately weren't needed and a few more grey hairs. I dont regret buying the Hawkeye though - brilliant bit of gear for working on these.

Pat