Hello everyone, I’m starting a new post as it seems I’ve finally narrowed my search for understanding why my engine is running rich with a poor idle. After changing both cats and all 02 sensors I can see my bank 1 upstream sensor amperage readings are jumping from very high to normal until it finally shuts down and a P1646 pops out. Wouldn’t that point to a leak? As far as I can see I have no obvious leak… Any ideas? Any suggestion would be most welcome !!!! Thank you everyone ! Note: I have sometimes a whistle when I decelerate and car RPM is about 1500.

 

It is normal for an upstream sensor that its voltage (not amperage) jumps all the time between 0.1 and 0.9 volt. What voltage readings are you getting? What is it that you consider "very high" and what do you consider "normal"?

 

B2S1 jumps from -0.64 mA to 0.20 mA and B1S1 jumps from -14 mA to 9.43 mA. I’d say B1S1 is fine but there definitely something wrong on the other side and it isn’t the sensor nor the cat. Has anyone seen this? Thank you!

 

Could it be an exhaust manifold tiny leak?

 

Yes when sensor is narrowband. Wideband is a whole another story as you probably know.

 

I’m totally lost with these sensors… it seems simple when explained on video but at the end I realize I don’t really understand the thing…

 

isn’t the aj27 wideband?

 

Where/how are you reading these mA?

 

AJ27 is 4 wires wideband in my understanding… I read the data on the OBD scanner….

 

Cars with wideband sensors It is waaaay easier to read only downstream sensors. It gives good enough measurement from the fuel mixture. Reading wideband heater currend deviations is kinda useless. AJ27 uses 4 wire widebands as upstream sensors.

 

Ok, so what do you think about my erratic readings on B1S1? Exhaust leak before the cat?

 

P1646 Heated oxygen sensor 1 (upstream), bank 1 – control malfunction
Possible faults: heater failure, sensing circuit: short circuit to ground, short circuit to high voltage, open circuit, ECM Failure
Before digging into leaks i would thoroughly triple check if sensor and its circuit is ok

 

Yes i have the codes PDF too and trust me when I say it’s been checked thoroughly. Or so I believe. It’s definitely not the sensor. I have 2 sensors and it’s the same. If it’s the loom: I’m out of ideas for testing it. No visible damage, voltage is good. Connection to the ECU is clean, relay was tested and responds fast. Any test you can recommend?

 

what brands of sensors you have there, are they oem or aftermarket, new or used, are both banks sensors the same pair or each is different?
if you swap right and left sensor plugs in bulkhead sockets and error moves to other bank then it would point to sensor or whereabouts if error stays then i would bet on loom or ecu

 

You can ohm the wiring with sensor disconnected but 2 bad sensors (say both the same but wrong kind) sounds most likely.

 

What is short term fuel trim doing at the same time and and what is downstream voltage at the same time per side ?

 

Thanks so much for looking into it: I have one new Denso of the correct ref for the car and one new aftermarket guinea pig. Both show the same readings. Bank 2 is fitted with a denso. ST Fuel trims are consistent with the erratic sensor reading and jumps abnormally compared to bank 2. LTFT is -10 on bank 1 and -3 on bank 2. I’ll check the grounds again tomorrow…