fault code

What prompted the reading of codes ? Did a light or message come up ?

For me the default is to clear the code or codes having saved them then disconnect the battery for a few minutes then re connect and see what happens .

Autel reader ??

After you cleared the code did it return ??

I’ve not had any on my current car but had a few on my T180. I always cleared them did the reset mentioned above and not once did they return. Seems to be a Toyita thing .

Well, stating the obvious, the one DTC has probably lead to the other.

C1299 is kind of related to the control of the solenoid/clutch in the rear diff. It wouldn't be too unreasonable for that to be due to the reported low supply (as indicated by other DTC).

Alternatively, maybe a problem with the solenoid itself has pulled the local supply in the 4WD ECU down (not a direct short, which would be likely to blow a fuse) and generated the abnormal power supply DTC along with C1299.

C1299 can also be generated by differing rolling radii of the wheels/tyres, but I suspect that is unlikely due to the abnormal supply voltage DTC also being present.

If it happens again, maybe check your alternator output (but I suspect it's OK, as other system on the vehicle would probably have complained about high/low voltage too).

Maybe check the two fuses shown.

You could also check the supply voltage at the 4WD ECU connector (E67), but if the supply voltage is being pulled low at that point, it will probably need a load (i.e. the ECU and solenoid via the ECU) on it to show, so just measuring the voltage at the connector pins, with the connector disconnected from the ECU, may well look fine and tell you nothing. The 4WD ECU is somewhere around the knee airbag area, probably more towards the drivers door.

Personally, I don't subscribe to clear DTC and disconnect the battery. Clear the DTC first, then see what happens. A healthy running ECU should not need a battery disconnect and diagnosis is always hindered by doing more than one thing at a time. If the DTCs come back, then try clearing and a battery or connector disconnect, in my opinion.

Good luck.


4wd by sh cm, on Flickr

E67:

90980-12422 by sh cm, on Flickr

C1299 can also be generated by differing rolling radii of the wheels/tyres, but I suspect that is unlikely due to the abnormal supply voltage DTC also being present...../ might be got a puncture on the 17tns....replaced with 16tens ...one wheel only...replaced with two directionals on the back 17tens again...so both 17tens again....then got the code afew days later.

i wounder if the voltage was stored to change batery last year>?