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2001 wrx pro drive
so this car has been in a shed for 7years and many gremlins. so far found the MAP sensor had 2 pins round the wrong way
broken wire to a injector
now the next one has me stumped
bank 1 sensor 1 heater control circuit low
changed sensor for denso one. still the same , same code even if I unplug it or not
pin 2 has 12v to ground so im assuming that the main relay is working
when I go to live data on my laptop I can only see inso for rear o2 sensor
front ones does not even appear on the list , is this because the ECU cant see it ?
ive ensured the sensor had a good earth . so its not that
how do I test the remaining 3 wires and what am I looking for please
this I think is the last issue I have. ( I hope ). thanks
On the A/F sensor, Pins 1(output)&2 (input) are the Heater circuit; Pins 3&4 are the sensor signals.
The heater circuit is controlled by the ECU putting sensor pin1 to earth via ECU pins 4&5 and out through ECU pins to earth as shown on diagram. Same voltage at ECU pins 4&5 whether sensor is plugged in or not "could be" an internal ECU circuity problem although putting 4&5 to battery voltage would switch the heater to off.
Basically to check if the heater is working you need to measure the resistance across sensor pins 1& 2 and also check the current flow when heater is switched on, and whether ECU pins 8&9 have a good earth as per DTC.
let’s hope that’s all it is.
makes more sense now tho. The live comes from the relay. And the negs are switched by the ecu. So if the ecu makes continuous to earth then the voltage reading at the ecu should be very low. By it being 12v that means it’s not going to earth at all. Thanks
there is 12v from the relay to pin 2 thats a black wire
then the lambda ( even tho its incorrect ) passes the 12v through the heater element and back down the other black wire to the ecu where is still has 12v
pins 8 / 9 are straight to earth no issue there
what controls the ecu to make it send 8/9 to 4/5 completing the circuit
at the moment this is not happening . but as I said its the wrong lambda . could it be the resistance of the heater element incorrect and the ecu detects this ?
how likely is it that the ecu itself is at fault ? id like to hope it isn't
the ecu in the car appears to of been out as there is writing on it in permanent marker or is this poss its to do with the pro drive
sorry for all the questions mate but if I need to replace the ecu im bu@@ered ad this wont be cheap in any way
thanks
AFAIK: "Most" Prodrive Performance Packs were Dealer fitment, so the ECU would be sent to Prodrive for re-flashing and then returned.
As for the "actual" method that the ECU uses to control the Heater circuits, I cannot say as I do not know. It may stay on continuously whilst the engine is running or it may be switched off when the exhaust temp reaches the correct temp.
General Subaru info on O2 Sensors attached.
Why not wait and see the outcome on fitting the new sensor and clearing any codes in the ECU.
Last edited by Don Clark; Mar 24, 2025 at 07:08 PM.
EML light is off after fitting correct sensor
YAHOOOOOOOOOOO
a Massive thanks to @Don Clark for his help
1 step nearer
How ever since the correct lambda sensor is installed im back to where I started a massive hesitation issue when I try to rev engine , with out any load on .
with the eml light on it revved up well . mmmmmmmm. never can be easy. ha ha ha
Having read through your other threads the REAR O2 sensor (p/n 22690501) is in fact the DOX-0357
Given it's 7 year hiatus may be worth investigating the following, if you haven't already covered them.
Did you clean the air intake temp sensor on the side the maf?
May be worth cleaning out the IACV and replacing it's gasket. (may be sticking)
A few part numbers:
Item 6 - purge control solenoid valve
slowly winning
