My 1993 124 Series 320E is experiencing intermittent problems where it refuses to switch from 4th to 5th gear. Win Star engine diagnostics reveal fault code 06 Can, which initially suggested faulty ECU, Wiring Harness and Data Bus link. All these items have been replaced and the ohms across the various circuits tested as ok but the fault still persists and seems to trigger when the engine revs above 3000rpm. A test loom has been connected to the ECU which seems to alleviate the problem at least for a while but the fault eventually returns. A donor vehicle is available and we have tried all the other ususal usual suspects such as changing the gearbox control unit and the idle speed actuator, all to no avail.
Any ideas or advice would be greatly appreciated.

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1993 320E 5 Speed Auto Sportline

I'm not sure what part of the world you live in...but in the U.S. the w124 automatics were all 4spd. Perhaps you meant its not changing from 3rd to 4th?

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE

I forgot to mention that I live in the UK and the 5 speed Auto was a popular option on the 300E 24V and 320E from 1990 onwards.

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1993 320E 5 Speed Auto Sportline

Hmm...while I'm not that experienced with transmission debugging (thankfully I've had no major problems with our transmissions) most people suggest to carefully inspect the vacuum lines going to the tranmission. Cracked/leaking/broken vacuum lines have been known to cause a variety of tramission maledies so I would start there. Sorry I can't be of more help...perhaps someone else with more experience will post to help you out.

BTW: Do you know what transmission you have? (Ex. the 94 E320 US model was a 722.369) This might be useful for doing a search if you could locate that information.

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE

Have you tried a known good EGS control unit? Also, is the kickdown working properly? On this side of the pond the 722.5 had a variety of problems, kick down and/or 5th gear not operating correctly were the most common. Some of those problems were solved by replacing the Base Modules, others by replacing the solenoids in the transmission after burning up the replacement Base Module (140 Chassis) Some other 722.5 problems were solved by replacing the EZL control unit as it lacked the output signal to the EGS control unit (129 Chassis) The harness and the two solenoids inside the trans are often overlooked as potential problems. The 129 EGS control unit powers up Y3/1y1 an Y3/1y2 solenoids, if one of them is shorted I imagine that you may need a new EGS unit as well.

Since I do not have a wiring diagram for your vehicles particular configuration I will not be much help beyond the following statements. If your vehicle is wired as the US version 129 chassis you might want to check the voltage supply to the EGS (socket 21 for US cars) with the engine running. The OVP relay powers up the EGS over here, I can’t imagine that it would be much different over there!

Take care, good luck and hope fully someone from the other side of the pond can assist you with more details. Hopefully your problem is just electrical, if it is mechanical be prepard to part with some of the family jewels.

Hiya guys!
Got a vehicle here with exact fault, found microswitch faulty in the gear selector, replaced it but no joy still ahhhhh! Does anyone know where the egs module is located?? cheers Carlo@ss