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If the near-stalling coincides precisely with the radiator cooling fans switching off, then I think you may have a problem with back-emf. Back-emf (electromotive force) is the phenomenon commonly known as a voltage spike, which occurs when the current to an inductive load is switched off. Even with a supply voltage of only 12V, this spike can easily reach hundreds, even thousands, of volts.

The spike is negative-going, meaning that it will have the opposite polarity to the supply voltage, and its duration will be very brief - typically just a few milliseconds. Because of its short duration you wouldn't see it on a multimeter, aside from maybe a momentary fluctuation in the meter reading, but it's observable on an oscilloscope, and with a digital storage 'scope it's possible to capture the waveform and analyse it at one's leisure.

There is a path from the positive terminals of the fans, through fuse 'W' (10A, engine compartment fuse box) and into the PCM on pin 4 (Fan Monitor Input), so a spike could be reaching the PCM via that route.

There's also a path from the coils of three relays within the CCRM - the EDF, HEDF1 and HEDF2 relays - into the PCM on pin 17 (High Fan Control), so a spike could be reaching the PCM via that route also.

The back-emf protection for the three (inductive) relay coils within the CCRM is clear to see - they're protected by a single reverse-biased diode, so if that has failed then for sure a spike would reach the PCM.

The back-emf protection within the fans isn't shown. They will likely be brushless DC motors, having a series of (inductive) coils fed via a solid-state current-switching circuit. Each coil will be protected locally by a reverse-biased diode, but in the event of a failure of one of those diodes, I don't know what the chances are of the resulting spike escaping from the motor. The circuitry will be relatively complex - solid-state current switching, current amplifiers etc., and I don't know if a spike could get past them without destroying them in the process.

Faced with this situation, I'd probably just open up the CCRM and check out the diode. It won't have failed short-circuit (if it had, it would interfere with relay operation) but it could have failed open-circuit or the soldering could be dry-jointed (cold joint). PCB track damage would be a less likely possibility too.

If the CCRM had awkward access or looked like it would be a problem to open, then I'd temporarily fit a reverse-biased diode externally.

If the vehicle still nearly stalled when the cooling fans switched off, then I'd remove that temporary diode from the CCRM and temporarily fit a reverse-biased diode across the fan motors - they're wired in parallel, so a single diode would protect against back-emf from either, or from both.

It's possible that you don't have a problem with spikes at fan switch-off, but if the voltage feed into the fans, and the ground path leading from the fans are both good, then that's what I would be looking at next.

I won't go into detail on hooking up the diodes because this post is long enough already, but if you want to proceed with that at any time then let me know and I'll explain more fully. The diodes required would be cheap, and readily-available types.