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You need to check the front sensor on the rear exhaust manifold. That is bank 1 sensor 1 which is what you have the code for. Also inspect that harness where it comes up and hooks next to the purge valve. I have seen the harnesses rub against the valve bracket and short out.
Hi Richard. have checked wiring visualy. no chafing. have run engine ,vigouresly moving loom wires,fault did not show. Switch of engine,re start eng man light on after 7 seconds ..... every time. so first run ok subsequant run, fault apears.where do i look next.
Thanks for the accept. The light comes on when you restart the engine because the ECM needs to detect the fault on 2 trips to turn on the light. I just re-read your post and the sensor you need to look at and most likely replace is the front sensor on the rear exhaust manifold with the grey connector. You shold make sure that you have battery voltage at the white/green wire.
The code P1646 is for bank 1 sensor 1 which is the front sensor in the rear exhaust. It should be the one with the grey connector.
Dear XXXXX.I have replaced the sensor you described ,cleared the code a . job well done. Many thanks .Tom