Car only starts when primary 02 is unplugged

[j0hnnybk01]

Hey all . So i recently installed a speed by design turbo kit and now my car wont start unless the primary 02 sensor is unplugged . The MAF seems to be working . It reads 0.75 at idle and goes up when i hit the gas a little . I have never ran into this issue before . Can anyone help me out ?? Really need my car up and running by tomorrow afternoon .

[brentjones518]

Could mean that the o2 is damaged. Have you tried plugging it in after you start the car? You need to somehow test a/f ratio. Or try a sensor off another Frs/Brz if you know someone near you


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[Spartarus]

Here's my bet:

I'm very familiar with the wiring in this car. The high-current pair in that sensor is the sensor heater circuit. It's run off the EFI MAIN2 relay. I'd bet money you damaged the wiring installing it and hard-shorted the heater circuit.

The highlighted 15A fuse will be blown. Pic related.

If you're (very) unlucky, the fuse immediately above it [EFI(CTRL)] will be blown. That's the fuse for the switch circuit side of the relay.

If there are fuses blown, you need to examine your o2 sensor wires. It may be repairable, but if you short the heater side to the signal side, you will be feeding a maximum of 15 amps into a sensor circuit in the ECU that is designed for a range of -1.0 to +0.5 milliamps. Good news is it starts with the sensor unplugged, so your ECU is intact.

[chaoskaze]

Dude! Spartacus, how much point did you put in int to become the mysterious stranger himself & oneshot any question that comes your way?


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[j0hnnybk01]

All fuses look good and none of the wires on the 02 sensor seem to be damaged at all .

[j0hnnybk01]

i can plug it back in but i think the af ratio is 14.5 but when i try to rev it it changes and wont rev

[steve99]

Originally Posted by j0hnnybk01

i can plug it back in but i think the af ratio is 14.5 but when i try to rev it it changes and wont rev

assume you have blabk plug to black socket and grey to grey as the front and rear o2 sensors can fit in wrong socket.

assume you have turbo tune loaded with matching MAP sensor ?

with the 02 sensor unplugged ecu likely goes into limp mode and ignores a lot of sensors and just runs in limp super safe mode maps.

when you plug in sensor ecu likely tries to run normal mode and fails possibly due to some other sensor input problem.

so it might not actually be the o2 thats the problem , although it could b damaged, did you use a lot of force to remove/reinstall it they should screw in by hand, excess torque can break them, best to run thread tap through fittings.


check you have correct tune loaded and correct map (pressure sensor) scaling to match map and tune. check MAF sensor is also connected and any extension harness is good.

use your OFT or other tuniing device to read cel coded from ecu and look at sensor inputs.

make sure your not running an E85 tune on petrol or petrol tune on E85

have you changed injectors ? are correct injector scaling loaded in tune ?

[j0hnnybk01]

yes grey plug to grey and black to black . Tune matches the new 3 bar map and map reads correct 14.35 was told it should be around 14.5 . Was not rough with the 02 it came out pretty easy and when i installed it i just snugged it on . maf is connected . I am running stock fuel pump and stock injectors . 02 seems to be fine no exposed wires or loose pins no burns at all . I also unplugged the battery for an hour and still no luck . only code i can get from the ecu now is p0013 only because i unplugged the 02 to start it.

[Spartarus]

Start it with MAF unplugged instead and report back.

[DustinS]

When it's running in Limp Mode, Check what MAF Voltage is at as well. (The Maf will need to be plugged in for this to work obviously. So try Spartarus suggestion first).

I had an issue with a MAF wire pulling out of the plug, Would cause the Maf voltage to drop to 0 at times. Check to make sure all the wires going to MAF are seating in the plug completely and can't be pulled out.

[steve99]

Originally Posted by j0hnnybk01

yes grey plug to grey and black to black . Tune matches the new 3 bar map and map reads correct 14.35 was told it should be around 14.5 . Was not rough with the 02 it came out pretty easy and when i installed it i just snugged it on . maf is connected . I am running stock fuel pump and stock injectors . 02 seems to be fine no exposed wires or loose pins no burns at all . I also unplugged the battery for an hour and still no luck . only code i can get from the ecu now is p0013 only because i unplugged the 02 to start it.

ok p0013 is camshaft position sensor bank 1, not o2 2sensor. Check the plugs on cam sensors on front of motor both sides they break easy

[j0hnnybk01]

My bad p0031 was the code . @Spartarus i can only start it with 02 unplugged still . If i leave the 02 in it wont start . if the MAF and 02 are both unplugged it starts . If i try to rev it with MAF unplugged it shuts off right away .

[steve99]

Originally Posted by j0hnnybk01

My bad p0031 was the code . @Spartarus i can only start it with 02 unplugged still . If i leave the 02 in it wont start . if the MAF and 02 are both unplugged it starts . If i try to rev it with MAF unplugged it shuts off right away .

looks like it might be maf related, does the kit use a maf extension cable if so check for continuity on all pins and connectors. Check maf not dirty oily or got crap stuck in it etc

should see somewhere arround 1 to 1.5v at idle for maf volts

are all the engine earth connection put back if removed.

[j0hnnybk01]

Maf reads 0.75 at idle and responds to the gas pedal . There is a chip on the tube part of the maf but i dont think that would matter . I got a 02 today ill try it . If not ill return it for a maf .