ep3 check enginie light
 

I have an 02 si and my check engine light came on yesterday. So I brought it to auto zone today and this is the print out.
primary HO2S (no 1) heater system electrical probable cause
1. open or short circuit condition
2. poor electrical connection
3. failed HO2S sensor

the guy that worked there told me to check all my sensor's and none of them looked bad. Has anyone had this problem and does anyone have any ideas??

thanks a bunch
Zach

Re: ep3 check enginie light
 

you prob wont be able to "look" at the sensor and tell if its "ok". the best thing would be to get an obd2 scan tool, and watch the o2 sensor graph. if you dont know what that means get a tech to do it. otherwise you could always replace the sensor. or get the specs on what the sensor should be operating at, and get a fluke and start testing resistance between wires and volts to the sensor

Re: ep3 check enginie light
 

try this if you want the check engine light off.
1. Do not start an engine. just ignition on
2. Push and Hold the miles reset thing for 10 sec or more til the check engine light off.
3. off the ignition and start the engine and running.
4. waiting for check engine light go to be off. if it come back then there's something wrong with it.

Re: ep3 check enginie light
 

I have a EP, first thing I would recheck the connection to the primary. Make sure all the wires are in the harness connectors fully. Also check the wires running up the firewall. Theres a little plate looking thing the wires connect to, id say check them there aswell. Also check and make sure there sealing right. May need to clean them. ANother thing you can check is the AMP fuse under the dash. I think its fuse #14.

To get rid of the CEL, just pull the ECU fuse under the hood for about 30 seconds, I cant remember the number, but its a 20 amp fuse.

Re: ep3 check enginie light
 

A couple minutes with a multimeter is all you need to find out what's going on. You don't need to worry about looking at the O2 sensor signals, because that's not what's wrong. The CEL readout clearly says "heater circuit" so you just have to check out the heater circuit. HO2S means "heated oxygen sensor" by the way.

The heater circuit is usually 2 wires, one wire goes to 12V power and one goes to the ECU. The ECU completes the circuit to ground, just like your fuel injectors, etc. I'm assuming it's a 4 wire sensor..

Anyway, you should have 12v at the connector with the car on, which is easy to check. You can check continuity between the other wire and the ECU, and that's easy to do too. Then you can check the resistance in the sensor itself. I'm not sure what the resistance should be on the Honda sensors, so I'm no help there. If all of those things check out, you've likely got a problem with the ECU, which would be very rare.

I'm guessing that you'll find a wire fatigue or connector corrosion problem, or that the O2 sensor itself is bad. If you don't have 12V at the sensor, find out why (the sensor is bad, the wiring is shorted, etc) because if you don't fix the problem it will happen again.

Re: ep3 check enginie light
 

Yes, its a 4-wire.

O2 sensor upstream(before cat.) is bad. Common problem with these cars. It happened to mine too. Only problem is is that they are $200+ at the dealer, about $100+ on ebay.

DO NOT BUY AN UNIVERSAL.

Re: ep3 check enginie light
 

Yeah, universals never quite work right. Makes sense though, the ECU is calibrated for a particular model of O2 sensor usually.

Re: ep3 check enginie light
 

i appreciate all the advice fellas. i guess i'm going to have to start looking for an o2 sensor. easy to install??

Re: ep3 check enginie light
 

i have a EP3 and my shits all fucked up, welcome to the club :D

Re: ep3 check enginie light
 

great car only has 60*** miles. are you sure that is the upstream. hate to pay all that money for nothing