Q: Recently I changed all filters and oil. Everything was fine after that.
Three weeks ago I then changed my transmission filter, pan gasket, plug in electrical unit and trans oil. I had experienced a lockout and then an engine icon warning light which then became all warning lights and lockout at home. I added a quart of trans fluid and my lights went out. Then I did the transmission work after which every thing was fine for about 2 weeks. Now the lockout is back with all warning lights. After a mile or so of easy driving the limp mode ends warning lights except for engine icon go away.
From your description, it sounds like you’re experiencing intermittent limp mode with all warning lights, followed by a return to normal operation after some driving, except for the persistent engine icon. Given the recent transmission service and the behavior you’re describing, there are a few likely causes:
- Transmission Fluid Level or Type: Even though you’ve added fluid, it’s crucial that the transmission is filled to the correct level using only the specified ATF+4 type for the 722.6 transmission. Overfilling or underfilling can both cause erratic behavior.
- Conductor Plate or Transmission Plug: You mentioned replacing the plug—if the connector wasn’t fully seated or the conductor plate (inside the transmission) is failing, it can cause speed sensor errors leading to limp mode. These are common failure points on the 722.6 transmission.
- Stored Transmission or Engine Fault Codes: The persistent engine icon suggests that fault codes are still present. These need to be read with a scanner capable of accessing the transmission and engine modules (preferably a scanner that can read Mercedes-Benz-specific codes).
- TCM (Transmission Control Module): It may be intermittently losing communication, especially if moisture intrusion or wiring harness issues are present.
- Grounds and Battery Voltage: Fluctuating voltage or poor grounds can trigger multiple warning lights and limp mode. It’s worth checking for corrosion or loose grounds, especially around the battery and TCM.
Next Steps I Recommend:
- Perform a diagnostic scan to retrieve stored and current fault codes, particularly in the TCM and ECM.
- Verify transmission fluid level with the correct procedure (temperature-based dipstick measurement).
- Inspect the transmission electrical plug and conductor plate again for signs of ATF contamination or loose fit.
- Check vehicle grounds and battery condition.
Let me know if you’d like help scheduling a diagnostic or if you need support with any of the checks mentioned above. We’re here to help get your Sprinter back to full health.