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So I got a obd1 JDM b16 swap into a 97 ex civic. When I start it, I have a check engine light on, and when I checked it, code 41 came up, which Its just the primary o2 sensor. I recently replaced it when I got my 4 to 1 header just to be safe. As a result of getting a 4 to 1 header I had to extend the sensor wires to reach the bung. Still the sensor seems to be not getting power. So I checked the sensor itself and I had power to all 4 wires. Next I checked the extended wires I did and they all had power as well. Next I checked jumper harness I’m using and each wire had power as well. After a lot of head scratching I decided to check the wires at the end of the ecu side of the engine wire harness. When I did this I got power to 3 out of the 4 wires. The wire I don’t have power to is the heater wire. My question is, is it possible to have power to the wires at the sensor, ecu, and jumper harness, but not inside the actual engine wire harness? Iv been trying to look forums up online for weeks now and had no help in my situation, if someone could help me I’d really appreciate.
There shouldn't be voltage to all four wires. Next, the only way you get voltage at all four wires in some places and only three wires in other places suggests a problem in the wiring modifications that you made to lengthen the wires. Did you do this at the O2 sensor itself or on the engine harness ?
There shouldn't be voltage to all four wires. Next, the only way you get voltage at all four wires in some places and only three wires in other places suggests a problem in the wiring modifications that you made to lengthen the wires. Did you do this at the O2 sensor itself or on the engine harness ?
So which wire should have voltage then? I tested each wire while the car was running if that makes a difference. Second I extended the wires at the o2 sensor only because I didn’t want to hack up the engine wire harness. In these pics you can see where I cut and extended the wires
The two black wires should show battery voltage across them with the key on. The green wire should show ground. White should have an oscillating voltage of 0 to ~1V if the car is successfully idling in closed loop. If you look at the wire colors on the engine harness side of the connector you should have:
1) WHT: Signal. Should go straight to the ecu. D14 on OBD1 ecu, D7 on OBD2A, C16 on OBD2B. This guy is likely your culprit.
2) GRN/BLK: Sensor ground SG2 - goes up to the junction connector under the manifold (I can see it in your last picture above), then off to the ecu. You can also check this wire for continuity to the GRN/BLK wire on the ECT, IAT, or TPS sensors since it will be easier to reach something else in the bay. Doens't matter if the key is on or not for that check. This is second most likely to be your culprit.
3) BLK/YEL: Ignition Power from fuse 15. Should have battery voltage with the key on (run position). Also comes from the junction connector under the manifold. With the key off you can check for continuity from the BLK/YEL wire in C101, which is the big engine harness connector on the driver's side shock tower area.
4) BLK/WHT: Heater control wire. This goes straight to the ecu and the ecu grounds it to turn on the heater. A6 for for OBD1 & OBD2A, C1 on OBD2B. I don't suspect this is your issue or you'd have a code 43 instead of 41. Double check for continuity anyways though.
Get in there with your meter and start checking continuity between the ecu and the signal wire, and the ecu and the sensor ground too. Jiggle the wires around and see if you can affect the resistance at all. For whatever reason these sensors are really sensitive to wires being cut & spliced. You might try getting another known good sensor and a pre-made extension harness and trying again. I prefer Denso or NTK sensors since the OE ones are officially no longer available. Well made extension harnesses can be found for a few bucks on eBay.
The two black wires should show battery voltage across them with the key on. The green wire should show ground. White should have an oscillating voltage of 0 to ~1V if the car is successfully idling in closed loop. If you look at the wire colors on the engine harness side of the connector you should have:
1) WHT: Signal. Should go straight to the ecu. D14 on OBD1 ecu, D7 on OBD2A, C16 on OBD2B. This guy is likely your culprit.
2) GRN/BLK: Sensor ground SG2 - goes up to the junction connector under the manifold (I can see it in your last picture above), then off to the ecu. You can also check this wire for continuity to the GRN/BLK wire on the ECT, IAT, or TPS sensors since it will be easier to reach something else in the bay. Doens't matter if the key is on or not for that check. This is second most likely to be your culprit.
3) BLK/YEL: Ignition Power from fuse 15. Should have battery voltage with the key on (run position). Also comes from the junction connector under the manifold. With the key off you can check for continuity from the BLK/YEL wire in C101, which is the big engine harness connector on the driver's side shock tower area.
4) BLK/WHT: Heater control wire. This goes straight to the ecu and the ecu grounds it to turn on the heater. A6 for for OBD1 & OBD2A, C1 on OBD2B. I don't suspect this is your issue or you'd have a code 43 instead of 41. Double check for continuity anyways though.
Get in there with your meter and start checking continuity between the ecu and the signal wire, and the ecu and the sensor ground too. Jiggle the wires around and see if you can affect the resistance at all. For whatever reason these sensors are really sensitive to wires being cut & spliced. You might try getting another known good sensor and a pre-made extension harness and trying again. I prefer Denso or NTK sensors since the OE ones are officially no longer available. Well made extension harnesses can be found for a few bucks on eBay.
So I tested the 02 sensor for Continuity unplugged from the engine harness and the volt meter beeped.
Next I tested the white wire at the ecu with the key turn to on and it showed 0.40 on the voltmeter
Then on the engine harness I tested the black/green wire on the o2 sensor plug to the IAT black/green wire and the voltmeter beeped
Next with the key off I tested the black/yellow wire on the driver side plug it beeped and showed .009 on the meter
Last the black/white wire I tested and it showed 12.46 on the voltmeter plus my I tested and heater works fine.
Did I do these test right ? Also how do I know which wire is bad?
97 Civic O2 Sensor Heater Wire No Power
