NS centre diff lock light constantly flashing

[Aaron.ns]

I have just purchased a NS V6 auto, it wasn't going when I got it due to the transponder key not working. Now it's going the centre light flashes immediately after starting. It won't go into 4wd or low, any ideas please?

[nj swb]

Welcome to the forum, and I'm sorry your first post wasn't able to be a little happier.

This is typically a problem with switches on the transfer case not properly detecting the state of the transfer case internals, although the confusion can be caused if one of the shifter switches isn't working i.e. the ecu doesn't know which mode the case is supposed to be in.

The best way to troubleshoot would be with a MUT3, or other OBD device that will allow reading of the switches and possibly driving the actuator. If you're handy with a multimeter, you can probe the switches directly, but it's a pain crawling under the vehicle to do this.

In lieu of more advanced testing, try turning the ignition off, select a mode with the shift lever, then turn the ignition back on again. If the transfer case switches and shift lever switches both match at start-up, the flashing light should disappear. You'll need to try this for each mode e.g. turn ignition on in 2H, again in 4H, again in 4HLc and again in 4LLc. If the vehicle was never used in 4wd it's possible the switches are "gummed up", and a few cycles might be enough to "free" them - but I wouldn't count on it.

[Aaron.ns]

I tried to cycle through the various selections to no avail, starting ot also in each one. When I first turn the ignition to accessories the greens come on and a 4L beside them, once it starts the greens go out and the centre lock light flashes again. I will try looking at the actuator and solenoids tomorrow, the resistance across them should be around 40 ohms I read somewhere, does that sound right? Thanks in advance.

[erad]

Aaron: The system is vacuum actuated. If you have a split hose (or maybe one has fallen off?), you may not have enough vacuum for the actuator to move the rod, and therefore the next stage may not happen. This can give an ECU error message. Get a code reading for the appropriate ECU and this may give you some idea as to what is happening.


Firstly, get underneath, and have a look at the hoses to and from the solenoids (under the battery) and then see if the actuator rod at the front diff moves when you get someone to shift the lever into 4WD etc.

[Aaron.ns]

The problem is fixed. After disconnecting the actuator on the front diff and swapping the vacuum lines the actuator cycled the other direction. To be certain I got a mobile scan guy to read the fault showing a code 35 relating to the freewheeling clutch actuator on the diff, which works fine by switching the lines. Replaced the pair of vacuum solenoids under the airbox and the lights went green, all is well. Thanks for the advice.