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I tested the TIPM relays and fuses; all are good. Confirmed that J19 and K11 have power. Confirmed with Thinkdiag2 OBD that ECM can start and stop low speed fan. Watched fan control signal signal triggering correctly with an oscilloscope. Replaced the low speed fan resistor. Resistance in the fan wiring harness is low. I've searched the web and found lots of discussion on P048x faults, but often describing circuits unlike my T&C's.

What I haven't been able to discover is how the ECM decides that the fan is not working. Is it coolant temp? DC current levels in the fan circuit? If the latter, where is the comparator circuit? The TIPM rebuilders mention a handful of common TIPM faults, but none claim they can fix fan related faults.

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  • This is a mechanic's mechanic/technician and did a video on a T&C P0480; youtube.com/watch?v=winfXPvjtgQ
    – F Dryer
    Jan 13 at 21:36
  • @f dryer The fans and fan control circuits in the 2008 T&C shown in the video, are entirely different from the 2013, which has one fan, not 2, doesn't use a pulse controlled ground, has the low speed fan relay in the TIPM, and uses a giant temp sensitive resistor in the radiator shroud to control fan speed. I've watched this and many similar videos; none seem to discuss how the ECM in the 2013 senses and triggers P0480.
    – Taryn
    Jan 15 at 16:50
  • My bad for misdirecting as I thought some info may help from the video. However, if I'm not mistaken, the large resistor may be a current limiting type used to lower fan speed when circuitry selects it. Service manual descriptions and wiring diagrams are the best way to troubleshoot electrical issues. Is this resistor blown? While Chilton and Haynes are good, Alldata or Mitchell are excellent equivalents of factory service manuals for immediate online access.
    – F Dryer
    Jan 16 at 2:45
  • @f dryer You are correct re the “fan resistor”, the resistance is inversely proportional to temperature, thusly embedded in the radiator housing, it modulates fan speed. My mechanic and I both tested and replaced the resistor, which didn't cure the P0480 code. I have the schematics for this model.
    – Taryn
    Jan 27 at 18:13

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To my knowledge, the ECM doesn't check fan health and none is reported to it. The ECM will trip the relay for the fan to come on. It doesn't care beyond that, even if the relay doesn't work. The ECM just does its job to power the relay which then powers the fan. This is basically a dumb circuit, meaning there's no real information passed between the fan, relay, and ECM.

As far as the P0480 code, this relates to the power the ECM is sensing to/from the relay, but not the relay to the fan. This is just a voltage difference than what it is supposed to be. Not real information, but it knows something isn't right there.

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  • Thanks Paul. Is that the difference across the relay coil, or across the switched points? If either, I guess the fault would be in the TIPM, since i've swapped out that relay several times?
    – Taryn
    Jan 12 at 18:52
  • @Taryn - It could be something in the wiring, but it's going to be in the circuit going from the ECM to the relay (the circuit which activates the relay), not on the other side. Jan 12 at 19:59

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