Generation 1, P1636 error

You've got some post hoc, ergo propter hoc going on here. That relay controls the brake fluid pressure pump. It is interesting that the cooling fans stopped when you were tapping it, and you could then start the Prius, but the probability of complete unvarnished coincidence is higher here than the probability the hydraulic pump relay was spinning your radiator fans. (Somewhere in between might be the chance of your tapping affecting a nearby component that makes more sense, but there isn't even anything in that particular box besides the two brake pump relays and the IGCT one delivering power to the inverter, converter, and HV and battery ECUs. How do the contacts look in those relay sockets? Or perhaps, since you seem to have a brake pump issue mentioned in your other thread, if one of the pump relays is sticking and excessive current is being drawn, it could be pulling down the 12 volt supply enough for another ECU to complain about. This isn't impossible, but still mighty speculative unless you catch it in the act with a meter.)

Troubleshooting steps make sense when they give you a way to divide-and-conquer the diagnostic problem. For a P1600, you need to find an electrical fault that could be anywhere on a path between the 12 volt battery and the BATT terminal of the ECM. The EFI fuse is kind of in the middle of that path. The manual actually has you start by measuring the ECM BATT terminal voltage with a meter. (Is the ECM really getting low voltage, or does a flaky ECM think it's getting low voltage?) Only after you confirm the problem really is with the voltage arriving at the ECM, you might next take a measurement at the EFI fuse location. On a good day, that will tell you whether to focus upstream or downstream of there. Divide and conquer ....

... all of which is much easier when you actually avail yourself of the manual and the wiring diagram.

It's more of a red herring, as the brake pump circuit isn't related to a P1600 or a P1636; even if your car right now has some crazy combination of problems allowing the one to affect the other (and not just a coincidence, which still runs high on the probability chart), the likelihood that somebody else's car will also have the same freaky combination going on would be even slimmer.

Best bet is usually just to follow something pretty close to the recommended troubleshooting procedure in order, even when that doesn't feel nonconformist enough....

-Chap

 

I'm sorry, just looked at your name again, and I think I was confusing you with somebody else having the brake pump issue. That still definitely is the brake pump relay, though.

That's good information to add to the thread. And in a situation like that, anything could be happening. Maybe the brake pump relay really is turning the radiator fans on and off, because something got spliced to something in the collision repair. (Something like that could make your own experience quite explainable, though of course it wouldn't apply to anybody else's unmodified car.)

These can be challenging situations to sort out. Do you know how to access the wiring diagram? techinfo.toyota.com. It will give you all the wire colors, wire locations and routing, connector diagrams and pin numbers, all the info you'd need to get sorted out.

Keep in mind that Toyota's only got so many wire colors to go around and sometimes they do repeat on different circuits, so trying to work only from wire color without having the diagram to follow location and routing and distinguish from other circuits, could lead to mistakes like splicing things that weren't to be spliced. Perhaps something like that even happened during the collision repair.

-Chap

 

Do you happen to remember which connector was giving you problems? I am currently trying to solve the p1600 code myself and have been hitting a wall.

 

Which manual were you using to have troubleshooting directions I have access to mitchell prodemand but it does not seem to have info on diagnostic test for code p1600.117.

 

We have a wiki page for that:

Toyota Service Information and Where To Find It | PriusChat