Hello again everyone. This problem is kicking my a**. I have a code 43 that shows up a few minutes after I start the car, I'm assuming right after the car goes into closed loop. I tried to emissions test it after erasing the code but it failed for running rich. So far I have tried multiple O2 sensors and checked the wiring back to the ecu, all checks out good with no shorts or opens. Plugs look good, not rich. Ignition timing is spot on. Replaced injectors (they were leaking down anyway). Replaced the fuel pressure regulator and verified the pressures are correct. Fuel pressure is good, newer fuel pump and filter. Also, no cracks or leaks in the exhaust that I can feel or hear. Cleaned the throttle body and calibrated the TPS. Also tried another ECU with the same result. WTF? Any suggestions would be greatly appreciated. Does anyone know the symptoms of a bad MAP sensor?

 

What car?

 

How is your ignition system doing?
Plugs, wires, cap, rotor, coil.

Anything related to fuel and igniting the fuel can be the issue.
Seems you have covered all the fuel components.

 

The car is a 91 civic that originally had a d15b2 motor in it. The ignition components have been gone through pretty well also. Durring the swap I replaced the coil, cap, rotor, plugs and wires. Also have checked ignition timing several times. The strange thing about this is the car seems to run fine, plenty of power, no smoke.

 

P28 ECU? Describe how you did the open and short tests for the O2 sensor wires. Which wires did you test?

 

I have 2 P28 Ecu's that I have tried. I checked the wiring by unplugging the o2 sensor and testing resistance of all of the wires back to the ecu plugs also checking for shorts to power/ground. All had about .2 ohms resistance. Also checked for power at the Yellow/Black wire with key on engine off which had 12v. Sensor ground was good. I thought I had found a problem, because the white wire on the sensor harness did not go to the white wire on the engine harness. I depinned the sensor ground and the white signal wire and swapped them, but I still got the code.....

 

At this point I'm thinking that I'm going to have to check every sensor back to the ECU to make sure that I didn't miss wire something. I know there are a lot of knowledgable people on here when it comes to swaps. Are there any common mistakes made when wiring up a swap? I used the D16z6 engine wiring harness for the most part so I think its unlikely that any of the plugs are wired wrong, but who knows.....somethings not right. I also fished the Ecu wiring from the ecu through the firewall into the engine compartment from a junkyard car so the majority of the wiring is from a 95 civic D16z6. The body harness is still from the 91 civic though.

 

If all had 0.2 Ohms of resistance in the short tests, then there is a short.

Only two of the four O2 sensor wires pertain to code 43 - the Wht and Grn/Wht wires - so refocus there.

The Wht wire should have continuity and no short between the O2 sensor plug and D14 of ECU connector D.

The Grn/Wht wire should have continuity and no short between the O2 sensor plug and D22 of ECU connector D.

Give details about the blue text in your quote.

 

Thanks for your reply. I should have been more specific on the test. I was testing the resistance of the individual wires from the unplugged o2 sensor connector to the unplugged ecu connector. White wire to pin d14, green/white to D22, orange black wire to a6. The wiring itself has .2 ohms. there is not continuity when testing short to ground. The wires that I switched were the green white sensor ground, and the white o2 input wire. The wire colors on the o2 sensor i got were white, blue, and two black wires. the white wire on the sensor plugged into the green white sensor ground on the engine harness and the blue plugged into the white wire on the engine harness. I'm wasn't sure if the o2 sensor wires were different so I tried switching them on the engine harness plug. I thought this would have some impact but the code came back. Also, I have wired in a switch to the aux power to the ecu for the purpose of clearing codes, so in case you were wondering the codes were cleared after swapping the wires.

 

F**K YEAH I just figured this thing out!!!!!!! I was staring hopelessly at my exposed wiring when I saw the grounded sheathing for the white o2 sensor signal wire. I unplugged the sensor and retested for shorts to ground, still nothing. I started bending the wire and saw a .5 ohm short to ground. Uncovered all of the tape holding the harness together and sure enough, there was a nick in the white wire that when bent would touch the metal sheathing. When i unplugged the connector to check it I must have flexed the wiring so it didn't show up but when I plugged it back in it started to make contact. So far this looks like the problem, I'll try to go pass emissions and we'll see for sure. No check engine light when I definitely would have had one by now. Big thanks to RonJ@HT for telling me to look at those wires again.

 

Passed emissions and still no check engine light. Looks like that was it. There is a noticeable difference in engine performance with the correct air/fuel ratio. I'm very impressed overall with the d15B2 to D16z6 swap. Even with a bogus o2 sensor reading and running really rich as a result, the car seemed much faster and more powerful than the D15b2 motor. Its amazing what variable valve timing and multi port fuel injection will do to a motor that is basically the same size as the D15b2. It was definitely worth the frustration that comes with rewiring your whole car.