A place for more technical discussions. Please make sure you post in the correct section on the site, this way it keeps the site tidy AND ensures you get a more relevant answer.
Well, I can't find the CEL connector and it's got a standard OBD2 socket under the dash in the driver's footwell.
I did some more testing today. I hooked the oscilloscope to the cam sensor and it's output exactly matches the waveform in the service manual. To monitor signals I push a wire into the back of the sensor plug, through the little rubber seal. I prefer doing that to poking things through the wire insulation. I did the same thing to the crank sensor plug and it now appears to start every time. I'm not sure at the moment if it's the sensor that's playing up or the plug but it certainly looks like it's one of the two. I have a new crank sensor on order.
Looking at other evidence I think this engine has been cooked at some point. The heat could have damaged the sensor. I'm replacing the cam sensor as well just to be safe.
Some good progress there. If fiddling with the connector on the crank sensor then it sounds a bit like a bad connection, the plug might have been damaged with excessive heat.
I guess if the sensor isn’t too expensive then it makes sense to replace it as well.
Perhaps some contact cleaner or even WD40 will sort out the plug?
Robin
2020 blue SZ5 (one of the last to be registered in the UK)
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog
The connector looked pretty clean. I have unplugged it several times during testing and it didn't appear to make any difference. The only thing I did different this time was poking a wire in the back of the connector so I could monitor the sensor while it was plugged in. When the new sensor arrives I'll inspect the plug more closely to see if there is a broken wire then if it all seems file I'll give it a good dose of Electrolube EML. Unlike most contact cleaners it leaves a thin lubricating film that helps prevent corrosion.
Now I just need to fix the rust in the back and the rather worrying little bubbles of gas popping up in the radiator - looks suspiciously like head gasket <sigh>
Just a quick progress report on this issue. I put it on the back burner while I was doing the welding, head gasket etc. Today I pulled the contacts out of the crank sensor plug and found the wire on one was pretty green and corroded. I don't have any of those contact crimps so I cut the wire back and soldered it to the crimp. It appeared to work but on the test drive the auto box seemed reluctant to change up. When I returned from the test drive it again didn't want to start. I now have an OBDII adapter so I plugged it in and got a whole stack of fault codes, including throttle position sensor. I checked the throttle position readout and it was wandering all over the place, mainly around 70 - 100%.
On checking the sensor there is no connection to the middle pin. The sensor is toast. This actually explains a lot. Most ECUs will stop the injectors if you hold full throttle while cranking. This is to clear a flooded engine. With the throttle reading wandering around randomly it could easily put the ECU into flood clear mode. That would explain the strangely short injector pulses.
The high throttle reading would also put the gearbox into kick down mode, which explains the reluctance to change gear.
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