falcon93si

Hi all,

I've done a decent amount of reading on this topic, and I still can't quite wrap my head around what I need, so apologize if this has been answered repetitively.

Car - 1993 Civic 1.6 EX

My situation - car was broken into, ECU only was stolen (bastards). I got a replacement ECU (37820-P28-L01). Car runs fine with this ECU, however the runs the error codes indicating that the VTEC solenoid is not present (obviously, since car is not VTEC).

Car is in CA, and will not pass smog while CEL is on.

Please help! Which ECU is the proper fit for my car? 37820-P28-A01?

Former User

What CEL codes?

How do you know it's an ECU problem as opposed to a VTEC problem?

Does the car have the stock D16Z6 engine?

mk378

So at some point your engine must also have been swapped, because the EX would have come with a VTEC engine.

The "P06" is a non-VTEC variant of the P28, used in the DX model. They are like the P28 also automatic or manual versions.

You could also try to figure out how to do the opposite of this:
PGMFI.ORG - Grassroots ECU Development - Library . NonVtec-To-Vtec

falcon93si

Ok, checked the engine code, D16z6, so it IS a VTEC motor.

The codes were 21 (VVT and Valve lift solenoid) and 41 (Oxygen sensor heater).

My assumption that it must be ECU based stems from the fact that I had no problems/CEL codes before the ECU was stolen, and these codes only registered after the installment of the new ECU.

Thanks for the corrections! Much appreciated.

Former User

What's the head code?

https://honda-tech.com/honda-civic-d.../#post48684945

https://honda-tech.com/honda-civic-d...-here-3210150/

Check whether the VTEC solenoid is connected to its plug.

If you reset the ECU, do the codes return?

falcon93si

P08-1 is the head code.

This car was not originally a California car. Would the change from (what I gather) was a P28-A01 to a P28-L01 have change something with the solenoid/O2 sensors to cause the CEL codes?

Former User

falcon93si

The solenoid is connected, yes.

After completing the ECU reset (run engine to operating temp, leave off for 15min, run for 15min, turn off and restart), the only CEL code is now 41 (O2 sensor heater).

I'll run voltage checks on the O2 Sensor heater now, and return results.

Former User

falcon93si

With ignition turned to "on" without the car running:

12v when yellow with black wire is grounded

-150ohms when terminals C/D on the female side of the sensor pigtail are crossed, ohmeter set to 20 (not positive this is the correct setting, but could not get a reading on the 2000 setting).

mk378

Exhaust cold, key off, unplug sensor and measure the heater resistance (between the two wires on the sensor that are the same color, usually white or black). I think the spec is 10 to 40 ohms. Replace sensor if resistance is too high or open circuit.

Former User

The resistance reading should be 10-40 Ohms. Replace the O2 sensor.

Edit - too late. mk got it.

falcon93si

awesome, thank you guys so much for the walkthrough. Will buy new O2 sensor, reset ecu, and reply back if further problems.

Thanks!!

falcon93si

Update:

O2 sensor replaced. Still throwing Code 41.

There is battery voltage to the yellow/black wire at the heater connector when the ignition is on.

There is a resistance of 10ohms between terminal C&D on the new O2 sensor.

Where should I go from here?

Former User

Test the ground wire for the O2 sensor heater for continuity to body ground with key OFF versus in ON(II).

falcon93si

No continuity shown on any of the pins on the heater side while key in "off" position.

Former User

What about with key in ON(II) or engine idling? Are unplugging the O2 sensor and testing the wire harness side pins?

falcon93si

Yes! Green/white wire shows extremely low ohms (.03 or .04) when key in OnII and slightly negative ohms (-.01 approx) when the engine is on.

I went back after turn the key off, and tested the green/white wire again. It showed extremely low ohms (.03 or .04) this time. I must have gotten a bad initial reading.

No continuity anywhere else.

What does this mean?

Former User

FYI

The ground wire for the O2 sensor heater element is Orn/Blk, not Grn/Wht.

The power wire for the O2 sensor heater element is Yel/Blk.

falcon93si

Ok. I tested all 4 wires on the connector, and the only one with any continuity was the grn/blk. None shown on the orange/blk.

Just went and reconfirmed the above.

Former User

That's the cause of code 41.

Unplug ECU connector A. Do you see an Orn/Blk wire at pin A6? Post a picture.

falcon93si

Yes, I believe so. I took pics of both sides, to make sure. I believe the wire in question to be in the first pic, third from the right.

Former User

It's there.

Locate 14P connector C103/C212 on the right shock tower.

The Orn/Blk wire passes through this connector. The pins may not be contacting one another inside the connector.

Unplug it and inspect for corrosion or damage. If all looks fine, replug and unplug several times. Ensure connector is fully seated. With O2 sensor unplugged and ECU connector A plugged in, redo test (continuity to body ground) of the Orn/Blk wire in the O2 sensor connector.

falcon93si

I've been unsuccessful with getting that connector separated, and I'm worried I'll destroy other connections if I do.

Would this work:

Run a jumper wire directly from the O2 connector terminal (that connects to the org/blk wire) to the A6 port on the ECU to see if it turns the light off

If this works, then there is a problem in the circuit, and if not, there is a problem in the ECU.

Does this make sense?

falcon93si

or, check continuity between the heat sensor end of the orange/blk and the ecu side of the orange/blk. If there is continuity, there is a problem with the ECU, if not, there is a problem, with the circuit.

Would this be an accurate test?