Hey Oceanbrave, I just confirmed that both mirrors pan all directions and curbview works as well. Extend also works. The only thing that is not working is Retract of the mirrors. I also confirmed 12v coming from the DDM when pressing the Extend button, but zero volts on the Retract which confirms all of our findings.

I have a Tech2 and within Body > Special Functions I can see the Output Data go from "Idle" to "Extend" when pressing the Mirror Extend button, but see no change of status from "Idle" when pressing the retract button. Is there something else within the Tech2 I should be using?

 

Just to be clear, do your mirrors pan in the correct directions?

"Extend" will always work, "Retract" is conditional, first it parks the mirrors, then if both sides are sucessful it retracts the arms. So when you press "Retract" do both mirrors 1st succesfully move back to their neutral positions?

If the Driver Door Moudule and Passenger Door Module both fail to retract it suggests they are not being commanded to move. If either module had a faulty drive circuit then only the arm on that side would fail to move, there is no feedback of the arm position.

It could a fault affecting only retract i.e. the motor spins one way but goes into current overload/fault in the other direction. This could be drive electonics, the chip that controls it is an "ST L9949 Door Actuator Driver" which has a Full-Bridge 6A circuit specifically for arm control. Its a surface mount device which you can find on ebay (search for ST L9949) they come from Hong Kong and only cost a few dollars. I've shared this part of the circuit diagram for your analysis (my interpretaion so not 100% accurate) As all other door module functions are working you would expect only this device to be responsible, the key question is which door module?

I went to all the trouble of replacing the chip only to find it wasn't that!

Also you would expect a motor jammed in one direction would normally give some indication, noise or movement.



For me the TECH2 briefly displayed a message (think it was either LEFT or RIGHT) before going to "Idle" that's what prompted me to check the mirror-motor wiring.

Attached is the circuit diagram, as you can see the 4-off potentiometers play an important role in feeding-back mirror positional information to door modules.

I'm off from tomorrow for a couple of weeks.

 

Based on your feedback, i'm trying to rationalize how these things work.

On a high level 12 volts are sent over the Brown and Grey wires to initiate the folding motors. The polarity is reversed to reverse the motors.

On mine, the DDM is sending the 12 volts on the Extend function but is not sending it on the Retract function.

BCM is aware of the commands being sent by the DDM.

I have replaced my DDM with a known working DDM that is folding the mirrors in another H2 so we can assume the logic for the retract is not on the DDM but in the BCM; OR is in the DDM but DDM is not getting what it needs from BCM or PDM?

We know the fold function itself has no logic going back to DDM, PDM, or BCM as there are only two leads to the fold function and they are direct current leads without any signal information, so the "position" of the arm is managed locally within the arm. You mentioned the logic of the Retract is dependent on mirror pan to be properly working which it does in my case, but I'm not sure where that logic is being processed, PDM, BCM, or DDM. The plugs and connections are all correct on my truck and nothing has been re-wired. I'm wondering if the logic needs to be reset somewhere. It would not be in the DDM as I physically replaced that. Perhaps the PDM, or BCM? And if so, is the Tech2 capable of resetting it?

 

you might want to check your firmware. i think there is an update for a similar issue since you have a tech2 available.https://tis2web.service.gm.com/tis2web

 

What you say about "polarity is reversed" is correct (but the diagram shows the colors as Yellow and Light Blue)

Apologies, you still didn't answer the key point, that is after pressing "Retract" do the mirrors home to their safe positions?

You say the plugs and connectors have not been re-wired but what about inside the mirror housing themselves? (see passenger side blelow)


Those little push-in crimp connectors are so easy to get mixed-up.

The DDM L9949 bridge cct controls the arm direction by OUT1 & OUT2 (see PDF) and controlled purly via software. The BCU sends commands via the SERIAL DATA bus to the DDM, the DDM in-turn talks locally via another serial-clock bus to the chip. I can't say for sure but I suspect the BCU issues a command and then waits for confirmation, so when it instructs the DDM to "Home" the mirrors it waits until this job is completed before issuing the "Retract" command.

It's still possible the chip could be faulty in that one side of the Full Bridge is either permanently shorted to 0V or +12V, thus one direction works while the other direction instantly goes into fault mode.

You say you've replaced the DDM but as you say, what about the PDM? If this has damaged electronics the result could be the same (that would be a pain)

I'm not aware of any TECH2 functions that reset the Door Modules or even reprograms them, MixManSC might know, but its not something I've ever done.

This is a video of the full Retract and Extend operations which I hope helps

 

clsimmon This may be of interest.

With the TECH2 set to "Outputs" (DDM) showing both the "Mirror Folding Operation" and "Mirror Motor" (both Idle normally)

After pressing "Retract" the Folding Op stays "Idle" whilst the "Mirror Motor" shows its current homing operation e.g "Left or Right". Once completed it switches back to "Idle" then the Folding Op shows "Retract" until it too has completed

In playing around with the driver's mirror positions, I found at the extreme right the Retract Op becomes inhibited. All other extremes were OK, just this one position failed. Nudging the mirror back slightly allowed Retract Op to function again.

The passenger side works OK in any position.

This suggests that my driver's side Horizontal potentiometer is going out-of-limits when pushed to the extreme right, the point is it is possible to defeat the Retract Op, just as yours is doing.

In my case the Driver Side mirror mechanism has been rebuilt and may have been assembled wrong with the physical mid-point slightly off (so easy to do)

Try the TECH2 and play with the mirror positions. Note that pressing right moves the mirror inwards towards you and pressing up moves towards the sky.

This my be linked to your issues.

Good luck, keep me posted.

 

* Problem Solved! *

The BCM (or DDM as I'm not sure which one exactly) reads the voltage from the potentiometer before retracting in order to reset the mirrors back to the exact position upon extension. The reason is that there are 3 possibilities of the mirror (glass) position upon Extension 1) Memory User #1, 2) Memory User #2, 3) Last Position Assuming no Seat Memory is programmed.

If for any reason the BCM/DDM cannot see a voltage range from the potentiometer, the BCM/DDM can't properly record current mirror (glass) position and will not enable the Retract command to work.

Notice when reading the data from the Passenger Door Module, while the passenger mirror (glass) is a nominally centered, the data shows the potentiometers have 2.9v for the horizontal position and 2.6v for the vertical position



However, when reading the data from the Driver Door Module, while the driver mirror (glass) is a nominally centered, the data shows the potentiometers have 2.5v for the horizontal position and 0v for the vertical position




When I moved the driver mirror max height the potentiometer finally gave me 1.1v and the mirrors retracted!

To rectify the problem, with the mirror all the way facing up at 1.1v, I swiftly pressed on the lower half of the mirror until I could here it 'click' down a few notches until a got a read of 2.5 volts while he mirror is positioned in the nominal center. I think overtime, these mirrors get bumped and notched up to where the pontentiometers give a 0.0v reading in a nominal centered position which then prevents mirror memory and mirror retraction.

For those that do not have a Tech 2, and your mirrors are not retracting a simple test would be to move mirror (with the interior switch and not your hand) to the extreme Up, and try retraction; extreme down, and try retraction; extreme left, and try; and extreme right and try...and then do the same on the other mirror. You will of course have 1 to 8 chances. Once you find the position that enables you to retract, then notch the mirror (glass) a few clicks in the opposite direction until the mirror is once again somewhat centered. Retraction and Memory will once again work as before.

Oceanbrave, thanks for all your insight on this!

 

great job.

 

clsimmon

Good job, I admire your investigative skills!

As the Tech2 can display the potentiometer voltages, this seems a very useful key for diagnostics.

Team work!!!

 

For karenM, here is an updated and expanded view of the DDM window motor part of the circuit. Note I've changed the relay wiring slightly to be as I believe it should be.