I bought this 2000 Civic EX w/ B16A3 from a guy as a hobby vehicle to tinker with. I knew going into this that the swap was very sloppy and this vehicle needed some major attention as it was a non-running tow home purchase. I figured I was going to get it running use it as a fun commuter car for a while, eventually ditch the chassis, rebuild the engine and install it in something more permanent down the road with better curb appeal. Maybe slap on an old T25 I have and run 4-6 psi or something like that but that can all be decided later.



My assessment:

2000 Civic EX Chassis (OBD2)

2000 Civic SI ECM (P2T – OBD2)

1993 Stamp B16A3 (OBD1)

EX OBD2 harness spliced into the OBD1 distributor, injectors and alternator.

-He must have made all of his cuts and strips with a steak knife because damn it was bad

-Wires were obviously just twisted together using the thumb and index finger method.

-Some wires were exposed and not even taped

-Random wires going all over the place and it was not quality work.



The engine had some active codes and a bad intermittent shut down issue. I figured to start by correcting the jenky wiring job. Went through each connection and was able to salvage the harness (not the prettiest). I found a bad ground in the main harness that would cause the engine to die if touched. I thought that was the culprit. Repaired that connection but it quickly died again on a short test drive. Troubleshooting brought me to the ICM and the intermittent shut down issue was resolved.



I then started to go after the engine codes. P0135 O2 S1B1 Heater, P0141 O2 S1B2 Heater, P0335 CKP Sensor.



Bypassed the open crank sensor fault by splicing into the cam sensor circuit and P0335 was eliminated.



Discovered there was no O2 sensor on bank 1, bung on the DC header was capped off. I bought a new sensor and P0135 went away upon install.



Here’s where the rabbit hole begins… 02 sensor B1S2 did not exist. No harness on the chassis side, no cat converter and no bung or place to install. I pulled the ECM schematics and began to wire in the B1S2 circuit at the ECM using the links below as reference.



http://technet.ff-squad.com/wiring.obd2b.htm



http://ff-squad.com/wp/?p=395



Once wired in, I welded a new bung in the exhaust and installed a new 02 sensor for S2. I thought when the vehicle was fired up I would be code free. Well that wasn’t the case. Both P0135 and P0141 were active in the scanner and CEL was illuminated. Double-checked my wiring and couldn’t see what the problem was.



I assumed the computer was seeing too much resistance or I didn’t have the proper readings form not having a cat. I bought an adjustable de-fouler to run on B1S2 and couldn’t get both the codes to clear by swapping the included orifice sizes. I could get 1 to go off but 2 would be on, 2 to go off but 1 be on, or both on at the same time on.



I bought this simulator below for B1S2 wired it in and could not get code free. Bought another simulator for B1S1 as well and still have not been able to get code free.

I did set the amperage per instructions on the heater circuit. The modules appear to be working fine as any adjustments will read on the multimeter. My 02 sensors were drawing 5.7ma and I matched the modules to that number.



https://www.magnumtuning.com/en/detail/adjustable-oxygen-sensor-simulator/honda/civic-si#select-box-anchor



Yes I’ve checked fuse #15. At this point I’m lost and feel like the only way to kick these O2 codes is convert to a chipped P28 ECM and delete the O2 parameters. I’m not ready to commit to a new ECM and need to take emissions test this month. Any help or suggestions would be very much appreciated.

 

Post pictures of the primary O2 sensor connector (stock?) showing the 4 wire colors.

Please briefly summary how you wired the secondary O2 sensor to fuse 15 and the ECU.

 

It’s messy right now. Just using quick splices for testing. Wires running through the firewall to engine bay. Just checked voltage on both heater circuit plugs. S1 checks out S2 is open and no voltage reading on heater circuit. Checked for heater 12v at ECM pin and no voltage there either going out. Do I need to link something to the fuse? Wouldn’t the ECM already be in line with #15 for S2 circuit?

 

I’m just splicing into the wires at the ECM. Checked some connections last night. No voltage at heater 12V from ECM to sensor harness I mocked up. Feeling dumb.

I’m going to try robbing power direct at the fuse junction - go to heater element in sensor - and out back to control pin on ECM.

Schematics help thank you. Will report what I find soon.

 

Battery voltage should NOT go to the ECU. It should go to the heater element of the O2 sensor.

Not sure what you are saying here^ and how it relates to previous quote. Maybe you can clarify.

 

Correct I said that wrong. I’m going to double check pin B1. There should be power there.

Take power from IG B1 > heater > control A8

 

Not sure where IG B1 is. Why not use voltage from fuse 15 as intended by Honda?

 

confused at why you need a simulator at the primary

 

Just an update here the vehicle is code free wired sensor 2 into fuse 15 circuit. P0141 went away.

still had p0135 on and discovered too much voltage drop going into heater control at ECM.

Was reading full voltage at the sensor / simulator which by the way didn’t need. Only reading 2 volts at ECM.
replaced wiring and good to go.

code free! Thanks for the help.