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Randomly and regularly it comes up with Restricted Performance and suddenly slows and loses power...
I changed the coolant pump...
A bit more detail, please. Did you change the coolant pump because of the message? Or did you change the pump for some other reason, and then the message started appearing?
You mentioned the pump was replaced. Make sure you replaced the correct one, as there are two electric pumps on supercharged models. The "aux coolant pump" is found on all V8 models and primarily ensures adequate coolant flow to the heater core at low engine RPM. It only runs under certain conditions. The supercharger coolant pump is installed (wait for it...) only on supercharged models, with more details quoted from the link above:
"Somehow I got off on the wrong track with this. Code P2601 is NOT the Aux Coolant pump. Its the S/C coolant pump. Big difference in function and price. The S/C pump delivers coolant to the S/C intercooler, it's intertwined with the rest of the cooling system and the pump is on 100% of the time when the key is in the II position."
This is a new problem, only started after replacing the pump? If so, it would seem your new pump is drawing too much current.
Could be the new pump is bad from stock. Or since you mentioned it was an upgraded design, maybe it draws more current by design than the original pump did.
Check the big connector around the wheel well. You have to remove the wheel and liner or get it up in the air and go from underneath. Just follow the plug wires and they go to a big connector. On my 06 str that connection had very bad corrosion and i had to bypass it for the charger pump. Worked great after that
The company I got the pump from have offered to send another. I am going to swap over the relay before that and put a new fuse in. It did not blow when at idle as I checked the voltage either side. I wonder if it is worth putting a 20A fuse in..... What are your thoughts on that? Maybe the pump does take a little more current.
I will check the conncector for corrosion too, I have had similar on other cars causing small surges in current as it connects and breaks then connects. Will also check for chaffing.
Update.
Seems to be a pump failure. Strange being brand new, but these things happen (why always to me?).
It started and ran ok for a few mins, certainly 12V applied to it from measuring on the fuse F36.
I left it running 5 mins and came back to find the fuse had blown and the pump body too hot to touch. Coolant pipes were still cool so not hot from coolant.
Good find on the pump getting hot. It can be a troubleshooting nightmare to have new parts bad from stock, but you seem to have a good handle on it.
Re: The ignition coil relay. If you have a spare, it would not hurt to replace it. As you noticed, the intercooler pump gets its power supply from the same relay powering the ignition coils. And yes, the relay is obviously working, at least to some extent. But I also suspect the ignition coils are more tolerant of low voltage. Say the contacts inside the relay are damaged from arcing. I'm talking about the on/off output side, not the electromagnet control portion. The contacts could be switching on/off as commanded, but have developed enough corrosion so only 10v or so is reaching the coils. That may be enough for the coils to still fire (it's entirely normal for battery voltage to dip close to 10V with the starter engaged), but this low voltage could affect the pump.
Certain types of high torque electric motors can go into a weird failure mode with a reduced voltage supply. The motor still tries to put out X amount of force, but draws lots of extra current doing so. Extra current = extra heat, so maybe that's what you're seeing. Kind of a long shot, so don't put too much stock in it. But it wouldn't hurt to swap that relay with a known good donor and see if that helps.
Still, most likely it's just a pump that was bad from stock. The old one failed in a totally different manner, with a mechanical failure of the bearings causing excess noise. That pump was never blowing fuses. The new problem (blown fuses) didn't start until you installed the new pump.
Something else unusual I noticed: I didn't see any monitoring of the pump, so am unsure what flags the P2601 fault code. Nothing monitors the amp draw or speed of the pump. The ignition coil relay switched power on/off to the pump.
The only thing I could see is the supercharged models have an "Inlet Air Temperature 2" sensor, not found on normally aspirated models. See figure 03.5 here, towards the left at the bottom of the diagram:
Strictly conjecture on my part, but perhaps if monitors the air temperature downstream of the cooler. If too warm under given conditions, maybe it flags that as a pump failure.
Update.
New pump fitted. We tested it before fitting and all was ok.
Once it was on we put a new fuse in and checked the pump for operation (noise and movement) with the ignition on. All seems ok.
After 10-20 mins running the pump was warm to the touch and certainly not hot. The pipes were not hot yet, but then is was just idling while it was being bled.
The old pump was hooked to an external battery and there was just a spark upon contact and no movement in the pump. So it is a dud.
Will try a test drive later.
Pulled apart the aftermarket pump, it seems to have seized where the plastic was rubbing against itself. I presume the other pump they supplied has done the same.
What are the Bosch pumps like? Are there any good pumps out there?
We pulled apart the OEM pump too, that had a dodgy impeller so it seemed, but upon putting it back together its freed up and moved more air on power-up than the aftermarket one.
Test drive for 20-30 minutes, get home and the pump is red hot again...
One thought: The pump handles coolant at approximately 200F. Sounds like the pump has other problems, but being hot to the touch may not be a fault in itself.