My 2008 M35x just developed a weird problem. While I was driving, all of the lights and gauges on the instrument panel, the navigation. blower fan motor, etc... suddenly switched off and then switched back on after about 30-60 seconds. The car didn't loose power or shutdown when this happened. This occurred randomly at any speed including while sitting idle at stoplights. I was driving it around for about an hour and it did that the whole time. I'd checked the battery, alternator, fuses and everything checked out fine. I turned off the engine and restarted it about 50 times and it had no issues with starting. Then, I let it sit idle in my driveway and watched it doing that for an hour that is when I noticed there is a faint clicking noise seem to come from inside the dashboard whenever the instrument panel lights and gauges switched on/off. The sound is almost like a relay contacts opens or closes. I spent hours searching but couldn't locate the exact location where the clicking noise had come from. I am at the end of my wit. I would greatly appreciate any information or pointers to help me troubleshooting this problem. Even though the car is still driving great and accelerated just fine when I took it out on the highway, I'm afraid to drive it for fear of it dying in the middle of a busy highway stretch.

Thank you in advance for any help or suggestions you can provide.

Regards

That is a weird one indeed. Not sure anyone here has ever had that crazy thing happening. I would look at the FSM and possibly investigate the wiring for the BCM or IPDM.

My suspicion is with the Unified Meter and A/C amp unit which sits right on top of the CD deck inside the dash. The unit controls the combination meter (the instrument cluster) as well as has some connections with the multifunction switch and the Nav unit. It's possible to run a scan on the unit for error codes with an appropriate tool.

As Ilya has suggested, another possibility is the IPDM which controls the illumination you mentioned by an integrated relay. The IPDM is in the engine bay, and one wonders whether the click you heard was from the IPDM. This relay is served by one or two fuses in the IPDM, which should be checked.

Thank you Ilya and Costee for your suggestions. I'll will check the BCM, IPDM, and the Unified Meter and A/C amp unit in the next few days. I did more troubleshooting today with the ignition ON but didn't run the engine; everything seems to shut-off every 5-7 minutes for the duration of about 2-3 seconds. It acted the same way with the engine running so I think it's getting worse with regard to cycling ON/OFF. The car started and ran without any performance issues that I can notice.

Thanks again and I will report back after I have more time troubleshooting
Regards

A quick update: I ran diagnostics on the Unified Meter and the IPDM multiple times, the results came back no issues every time I ran them but the instrument cluster still loss power about every 2-3 minutes for a brief 3-5 seconds. So, out of desperation, I took out the IPDM and checked every single fuse, relays and connectors but found no issues. I even bench tested the unit for any loose solder joints under magnifying light, I wiggled every component on the circuit board but found nothing lose so I re-assembled everything and installed the IPDM back in the car. I drove the car for 2 days without the instrument panel shut off. I thought I somehow I got a miracle fix but now the issue start to return, not as frequent as before but every once in awhile. My thinking is maybe the main power feed to the instrument cluster panel connection is loose but I could not figure out where to check next. I consulted the service manual related to electrical power distributions but I am at a loss on where to start first. Please let me know your thoughts.

Thanks in advance for any information you can provide
Best regards,
SamW

Looks as if you still have to go back to the IPDM. Seems a section controlled by the tail lamp relay coil in the CPU is compromised. Check FSM sections LT-296-299 and PG-28/29. Specifically, check terminal 21 in the IPDM.

Costee

Thank you for your suggestions, I'll check the tail lamp relay and the CPU when I have the chance to take the IPDM out again. I will also review the sections that you mentioned when I'm not too busy. I'll update again after I'd gone through the processes.

Thank you for your help again,
Best Regards,
Sam

Just a quick update on my progress

After 3 months of off and on troubleshooting due to a shoulder injury, I got no where still. I checked the tail lamp circuitry and everything looks ok. Terminal 21 of IDPM is energized. I pulled the IPDM and bench tested it again, everything seems fine. I went ahead and re-solder all the solder joints in the IPDM just in case there was a cold solder joint some where. Plugged everything back in the problem came back after 15 minutes driving.

I used a stethoscope to help identifying the location(s) where the clicking sounds come from when the instrument panel switched off and on and the sounds seem to come from behind the fuse block by the parking brake pedal. FSM PG-12 showed there are two relays (Accessory and Blower relays) are mounted on the back of the fuse block but I couldn't figure out how to remove the fuse block to check the relays.

After spending more time reading FSM PG, it looks like the coils for both relays are fed by the PDU; that might explains the clicking sound when the instrument panel turned off and on. I tried to follow the schematics but I got lost since I don't know where to find the PDU in my car. Is it the same as the IPDM? What are M31, M16, and M70? My thinking is there is either a lose connection on M31 or the ground is my problem since when the instrument panel turned off, the blower fan, the AV control screen are also turned off. Please let me know if you have any suggestions on how I should continue with my troubleshooting. BTW, I thought maybe my battery is weak even though I had it tested out good so I went ahead and installed a brand new higher CCA battery since then but the issue remains the same.

Thank you in advance for any help you can provide.
Best regards,
Sam

M30 & M31: PDU
M16: Body Ground
M70: Body Ground. See PG-43 for the location of the grounds.
The PDU is in the inner recesses of the instrument cluster, i.e, you'd have to remove the cluster to access it.
Regarding the back of the fuse block , I guess there's some tangential reference here:
https://g35driver.com/forums/general-te ... ent-2.html

Costee,

WOW! Thank you for the super fast reply.

The information you'd provided will be very helpful when the sun come up and I can see better to troubleshoot again. Believe it or not, I read the FSM PG from top to bottom a few dozen times but apparently nothing registered in my brains until you pointed them out in your reply. I guess, the brains don't work as well after a few strokes. So, Thank you very much for your help and guidance. I also read through the link you'd provided but all the images/pictures are no longer available so I'll have to follow the steps very carefully so I won't cause any damages.

Thanks again
Best regards

CHeck the battery connections. May sound stupid, but I had a slightly loose terminal that shut down my car in the middle of the interstate in downtown chicago one night. Eventually started up again, then died again a few miles later. Took a while to troubleshoot as it was still connected/tight, just not fully secured.

cjstringer920 Thank you for the suggestion. That was the first think I checked when the problem started. During the span of 4 months of troubleshooting, I had disconnected and reconnected the battery a few dozen times and rechecked the battery connections as far as I could go and found no lose or frayed wires. I am planning on removing the instrument panel in the next few days and see if I can find anything lose in there. I took the car to the shop and they wanted to keep it for two weeks to diagnose. I asked them what will they do for two weeks they told me basically they will do whatever I’d done already but their diagnostic costs will be a few hundreds dollars. I said no thanks since the car is still driving good without any loss of power or performance. It’s just a little annoying when the instrument panel turned off and on so is the blower fan during the hot weather. I know it’s probably just a simple lose connection somewhere related to the instrument cluster since everything else is still working when that happened. The signal lights and indicators, headlights and all the related indicators still work, windshield wipers, emergency signal, dome lights, etc... are not affected

Thank you again

Quick update:
I removed and inspected the PDU and the Fuse Block/Junction Box. Both look okay, I also re-tested all the fuses and the relays (ACC and Blower), they all passed. Now, I am tracing the wires out of the PDU to figure out if any of them lose or fray but I need a little help with interpreting the pictures from the FSM, specifically PG FSM. For example, PG-35 & 36 talk about checking the PDU power supply and ground circuit. the steps have a table and the connector and terminals to check/test and on the right of the table is a picture showing how to do it. My question is the pictures showed the black and white sides of the connectors and the squares with the connector on the top left and the letters H.S. on the bottom right, can you explain which side is which? When I look at the terminal number, am I suppose to look at the end of the connector with all the wires or the side that plugs into the PDU?

Thanks in advanced for your help
Best regards,
Sam

HS means connector view from the Harness Side; TS means connector view from the Terminal Side. In this case we have HS, that means you,to use your words, "look at the terminal number...at the end of the connector with all the wires."

Costee,

Thanks again for a quick reply.
To make sure I understand correctly, when I put the probe on the connector, I should stick them in the back of the connector where all the wires go into the connector to get the correct positions of the terminal numbers, right? I sincerely apologize for asking such trivial questions to you. I can read and troubleshoot household electronic schematics even for audio/video equipment just fine but car’s electronics confises me. Household connectors are designated as male or female connectors and it’s easy to relate and most of the time there is a mark on the connector to designate which one is terminal/pin 1 but I can’t find the same marking on car’s connectors. Maybe I need new glasses !!

Thank you again for your help and guidance
Best regards
Sam

SamW wrote: ↑

Sun Oct 11, 2020 2:34 am

Costee,
To make sure I understand correctly, when I put the probe on the connector, I should stick them in the back of the connector where all the wires go into the connector to get the correct positions of the terminal numbers, right?

Yes.

Update:

After tearing down almost the whole front dashboard and related panels to perform troubleshooting, I finally able to reproduced the behavior by wiggling the wires and harness at back of the AFS switch. In fact, if I just turn ON/OFF the AFS switch rapidly, I can replicate the same behavior. I have gone back and consulted the FSM's but I couldn't find the relationships between the AFS and the instrument cluster except the indicator lights and the power source, which seem to work correctly when the instrument cluster has power. I also traced the wires from the back of the AFS switch to as far as I could go but couldn't find anything wrong with the wires. Could the AFS switch is malfunctioning causing voltage drop or a temporary short circuited making the ACC and Blower fan relays loss their power to the coils? It's pretty dark by the time I was able to replicate the behavior so I couldn't go on to check further. Please let me know if you have any insights on why that happened or what should I check next.

Thanks in advance for any information you can provided.
Best regards,
Sam

I really do admire your tenacity. For the full information on the AFS the FSM is LT, pages 110-161. The AFS has CAN ramifications so a number electrical gadgets are involved, and in view of this I do subscribe to your hunch that a failing AFS switch can cause the intermitent issues you have (Cf. daigram on page 117).
Maybe when all this is over I will advise that you get a scan tool that can run through all the modules in your car (there is an AFS control unit in your car that can be scanned, for example). This would assist in determinning sections to start with troubleshooting. For a relatively cheaper tool I'll suggest Autel's MaxiDiag MD808 Pro.

Costee,

Thank you again for your help and guidance. You cannot imagine how much I appreciate what you’d done for me. I learned A LOT from you. I also thank you for your patience.

I’m having a full day today but I will find some time to read the LT FSM as you’d suggested. I will also look at the Autel tool you’d recommended. It sounds like a great tool and will probably save me lots of hours digging around in the car.

Thank you again and best regards
Sam

Update:

I removed the AFS switch and tested it. It failed the continuity test between pin 1 and pin 4 (open circuit on both ON and OFF positions). I think the diode inside the switch might be bad. I'll have to order a replacement before I can continue with troubleshooting. In the meantime, can I drive the car with the AFS switch removed? Is it safe to drive it? I don't plan to drive it at night so I won't need to turn on the headlights. I also want to know would it cause other components to fail too since AFS has CAN ramifications? Based on my reading of the LT FSM, the AFS switch seems to only used to provide power to pin 3 of the AFS control unit and illumination circuitry but I am not so sure. That's why I asked. I guess a stupid question is the one that never asked.

Thank you in advance for any help or insights.
best regards,
Sam

I think it's quite safe taking off/disconnecting the switch. In fact, I should think it's a method of troubleshooting too. If with the switch off you no longer have the symptoms, then you have your man. I'm sure after going through the FSM you'd see the importance of having a scan tool that could at least read signals of the controlling modules. I'm surprised,though not alarmed, that the AFS light on the dash hadn't come on all this while to reflect that there was a problem with the switch. But then maybe that's because it was an intermitent issue caused by a cancerous diode. Again, with the switch removed or disconnected let's know whether the AFS light on the dash comes on or not. I should think if it came on then that means all's well with the AFS control module and the affiliated circuitry.

Costee,

Thanks again. I’ll drive it around with the AFS switch removed for the next few days while waiting for the replacement switch. I’ll update my findings when appropriate

Regards
Sam

Quick update:

Got the replacement AFS switch, installed it and drove around for two days without issues then the problem reappeared and acts the same as before. Such a disappointment! At this point I don’t know what else to do or try

At this point I'll have to ask for a scan to be done. Since you had reason to suspect the AFS, you could leave it disconnected and let's see what happens? If the symptoms recur at least we'd be sure that circuit is intact. If all else fails, I guess you'd have to invite in/take the car to some competent tech. Problems are there to be solved. This will.
PS. Bench test the new AFS to confirm integrity following the incident.

After a few months with intermittent loss of the instrument panel while driving, I also started getting intermittent problems with the push start button then one day I couldn’t turn the car to ACC, ON or started the car anymore. After months of troubleshooting and with the help with some great people on this forum, I finally found the root cause. It’s the iKey control module was the culprit. I replaced the iKey control module, reprogram the key and things are working correctly now.
Thank you all and best regards
SamW