to add to what lumberjack posted i'd like to say in my own experience working on zapi controlled systems i've seen issues in the same areas he spoke of but also you may want to check the connections where the cables connect to the controller and make sure none of them are loose at the standoff. You can grab the cable and wiggle it a little bit and watch the bolt and where the standoff comes out of the cover and if it (the standoff) turns at all or is loose at all then the stand off is broken away from its mounting and the controller will have to be replaced. If the cable is loose and the standoff is still ok then just tighten the cable back up.
These standoffs are cold soldered to the positive and negative plates inside the controller and can break loose if put under any abnormal torque when checking tightness during PM's etc.
I've also encountered some problems with the ribbon cables inside the controller that connects the circuit boards together, they can come loose from vibration. zapi came out with a bulletin at some point in the past informing all service personel about it and had instructions on how to repair this. Basically you remove the cover, put the cables back into their respective ribbon connectors and then apply silicone to the cable and connector so insure they stay in place. Just remember if you go into the controller be extremely careful when taking the cable nuts/bolts loose. Most of the one's i've seen have a hex shaped part of the standoff to put a wrench on so you can hold it in place while loosening or tightening it, by all means use this method and don't risk it otherwise.

I used to work on a bunch of MPB's. One area that seemed prone to failure was the wiring harness where it goes through the drive unit. In the above motor tests you might want to measure motor continuity from the control panel end AND at the motor. You might find a field cable broken where it makes the bend through the drive unit.

there are 4 different AL6 codes
these are the following conditions listed that trigger this code in these controllers
-Motor current levels do not exceed a preset minimum value while driving.
-High field current values measured by controller.
-Low field current values measured by controller.
-Controller detects motor current during standby mode.

Possible causes and test proceedures
* Damaged or loose electrical connections to traction
motor.
Verify electrical connections between tractionmotor
and controller.
* Traction motor armature resistance is too low.
Check traction motor armature for shorts.
* Controller is damaged.
Cycle key switch. Place steer handle in drive position
and select throttle. If the truck starts to drive
but then stops and presents code AL6, replace controller.
* Field wires are loose, damaged, or shorted.
Verify connection of field wires to motor and controller.
* Motor field winding is shorted or too low.
Check motor field for correct resistance and continuity.
It should measure approximately 0.5 ohms.
* Failure of current sensor in controller.
Replace controller.
* Failure of field current driver in controller.
Replace controller.
* Cable connection to motor field is loose or damaged.
Verify connection of field wires to motor and controller.
* Motor field winding is open or too high.
Check motor field for correct resistance and continuity.
It should measure approximately 1.5 ohms.
* Field current sensor in controller has failed.
Replace controller.
* Main contactor circuit damaged or disconnected.
Verify electrical connection between controller and
contactor.
Check contactor coil for correct resistance of 52
ohms.
* Field current drivers in controller are damaged.
Replace controller.
* Damaged controller.
Replace controller

Anyone come up with a solution to this? Got one in the shop now. Brand new batterys and unit wont operate. Proxy. Switch light comes on but no click. Nothing else works

I have a code 06 that intermittently comes up on a Yale walkie. I've checked wiring, replaced the batteries, but code comes up every other day on a daily used unit and unit shuts down. Anyone have advice?

ok thx.. motor is new in june, so is controller.. ill chk the cables real good

AL-06 is normally a motor connection problem, can be a cable, brushes or internal motor problem. The controller can also be defective.

Working on a yale pallet jack mpb040en24t24748 s/n b827n1416b Just need some insight as to what this code is. thanks in advance...
having the same issue with code AL06 !! help

any help would be appreciated this thing is intermittant and killing me.

you have a email i can send you info