2005 Chrysler Town & Country P0846 P0888 P0891 P0700: Transmission Relay Issues and TCM Concerns

Just a quick note—my vehicle doesn't enter limp mode, and it randomly shuts off. I've checked the transmission fluid, which appears normal and at proper levels.

Limp mode (also known as 'get home mode') is typically triggered by transmission issues—fixing those will resolve it. Random shutdowns are a red flag; check the O2 sensor code again, and ensure you've ruled out any electrical faults. The P0846 indicates a pressure switch circuit fault, P0888 shows a relay output always off, and P0891 points to a transmission relay that's stuck on. These codes strongly suggest a problem with the transmission relay or its wiring harness. Have you checked the trans relay? Also, do you have a remote starter installed?

I don't have a remote start system. All systems like cruise control, horn, and AC are functioning normally—except for random shutdowns. I've tested the E-ATX (transmission relay) at terminal 86 using a test light and confirmed it's losing power. The car doesn’t exhibit erratic speedometer behavior; instead, it simply shuts off. I’ve been told this could be due to faulty speed sensor inputs or outputs—though I'm not sure yet. Speed sensors are relatively inexpensive, so I’m considering replacing them. That said, I’m still concerned about a TCM issue since it can mimic throttle position sensor symptoms at high speeds. My next step is to disconnect and inspect the speed sensor connections. The transmission shifts normally and isn’t in limp mode.

You're referring to E-ATX as the transmission relay—correct. Terminal 86 receives 12V from the PCM, right? Have you tried swapping out the relay to test functionality? Are you using a scan tool capable of reading all diagnostic codes—including manufacturer-specific or ABS-related ones? If possible, I’d be happy to share wiring diagrams for reference.

Yes, I'm using a scan tool (purchased for over $100 at AutoZone) and it can read all available codes. The issue has worsened—now the relay is cycling on and off more frequently. When I press the ABS button on the scanner, it reports 'ECU malfunction,' 'hydraulic malfunction,' and low voltage. While I'm not an expert in these systems, I do have some hands-on experience as a DIY mechanic. The only warning light present is the check engine light—no ABS or other dashboard alerts. This makes me wonder if there's a deeper electrical issue between the PCM and transmission control circuits.

The $100 scanner is likely just a basic code reader—it may not support all manufacturer-specific codes, especially ABS or advanced ECU diagnostics. I recommend verifying with Chrysler's official diagnostic tools to ensure full coverage of codes. If possible, I’ll review the wiring diagrams later and provide more targeted guidance.