I've been getting a code 17 referring to the feedback system for several months now. I have replaced the spark plugs, o2 sensor (oem n350 unit), coolant temp sensor, gas cap, fuel filter, and checked the pcv and charcoal canister. I still get the code 17 driving down the highway. I even swapped a spare ecu and no change. Ran a new wire from the o2 sensor straight to the ecu with no change. Swapped an untouched stock throttle body too.

What else to look at? Fuel pump? Injectors? Tps adjustment? Wire harness? (better not be bad...)

Any tips would be appreciated!

 

17 is o2 feedback system..

 

Yeah but it's much deeper than just the o2 sensor. There are dozens of things that can cause the feedback system to act up.

 

i'm under the impression that if there is something that throws the o2 sensor off, that can also trip 17, so like air leaks, possibly a malfunctioning ACV, exhaust leaks?

 

The last time I checked my codes, my POS clogged exhaust was still attached and my split air was still cut. I can look and see if it goes away when I rebuild my exhaust later today with straight pipe and remove/block off the split air and my air pump belt. If it doesn't go away, I would say check your ACV and your MAF/AFM/whatever Mazda calls them on these cars.

 

I haven't checked the acv...

A little mechanical info about the car,


-stock na 13b with 208,000 miles
-castrol 10w40
-low mileage ngk bur7 and 9eqp plugs
-ngk wires with roughly 25,000 miles 2 years old
-full racing beat exhaust
-new n350 Mazda o2 sensor
-split air outlet open on intake manifold
-o2 wire ran straight to ecu
-acv untouched
- air pump intact
-faulty pcv valve removed, ports on filler neck ran to charcoal canister
-new fuel filter and cap
-new coolant temp sensor

so just a few slight modifications otherwise all stock.

 

split air outlet open on intake manifold.
Have you tried plugging that to see if that is the cause?
Just a guess.

 

You can't really plug it since air flows from the air pump in 5th gear right? I think I've tried that on previous rx7s and it just blew the vacuum cap off. Could it be that the split air pipe not being connected is affecting back pressure? It's a series 5 so I never thought I needed it... The rb presilencer is welded shut at the split air pipe inlet. At the same time though ove owned the car in this basic configuration for over 2.5 years and it just started the code maybe 7-8 months ago. So I'm leaning towards something not functioning properly like the acv.

I'll check out the fsm for a method to test the acv with my meter.

 

doubtful, the split air goes from the air pump to after the O2 sensor. so neither the afm or the o2 will see it.

but its possible that the ACV is stuck in "port air" which would bring air pump air before the O2 sensor... not very likely....

or maybe one of the anti after burn valves on the ACV, i've seen that... although its a huge vacuum leak so the car doesn't run

 

The Oxygen Sensor has a metal shielding associated w/the wiring. Did you address this aspect properly?

 

Backprobe the o2 sensor AT the ECU plug and go for a drive. See if there is indeed a input to the ECU from the 02 sensor or not.

OR........ backprobe the 02 sensor at the ECU plug and fully warm the engine up. Read the meter and see what the reading is. Should be b/t 0vdc and 1vdc.

IF it's reading close to zero at idle with fully warm engine, then pulll the Relief solenoids elect plug off and the reading should come up to approx .8vdc give or take. IF it does then the 02 sensor is indeed making a input to the ECU. IF the reading still stays low close to zero..........then pull the wire off the 02 sensor itself and read it with a meter at idle. Should read approx .8vdc if the Relief solenoid elect connector is off.

 

I probed it awhile back and got .4v-.6v roughly I believe. The shielded wire was giving a code too. It only needs to be shielded if it runs across the engine. I have a fresh wire running from the o2 sensor through the rubber grommet on the firewall where the ac drip line is straight to the ecu.