har_v

Has anyone seen this problem before? My 2000 4runner engine light came on.
It coded as p0135 and p0141. (heaters on 02 sensors)
Both O2 sensors were replaced and after a few starts it coded again.
Old O2 sensors Ohmed around 13 across black (heater?) wires suggesting that they were still good.
Relay? Fuses? Anyone have a suggestion of where to look?

Thanks in advance.

MTL_4runner

Were they OEM from the dealer or Denso brand?

Greedy

I had the same code (p0141) forever after my turbo conversion. turns out I had a short in the wire harness somewhere. I just re-wired the whole length between the 02 sensor and the ecu with new wire. No code since.

har_v

The o2 sensors were original from the dealer.
What is strange is that both are in error (heater function) yet they ohm ok.
With new 02 sensors installed and light reset....it coded again on second start. Same two codes.

Greedy

I think the code is reffering to the heater circuit, which means it could be a problem with the wiring to the sensors. Do you have access to a FSM? Have you tried to establish connectivity between the sensors and the ecu? I believe the sensors do go through the efi relay, also, check the ground on the drivers side of the intake manifold. It is held on by a screw, make sure it is clean and tight.

har_v

Ground wire on intake manifold was the culprit.
My sincere thanks to Greedy.