kimbler99

its a 99 dx coupe with a obd1 ls using my stock wiring harness. car runs fine nice and smooth just can't get it to pass pa inspection with that light. tried a new o2 but no luck any ideas before i just get a chipped ecu and delete it. thanks

delsolintegra

Might be a hairline crack in the exhaust manifold next to the 02 sensor hole.
This happens on the D16Z6 engines. It causes the code and the cel light on the OBD1 setups (P28 ECU's).

If that's the problem I got a cheap header off ebay with a new downpipe for $60.

kimbler99

i got a 4-2-1 header and its leaking at the flange where it goes from 4 to 2. you think that might be my problem.

HondaPartsHero

delsolintegra

That crack sounds close enough to the o2 sensor to cause it.
A crack before the O2 sensor will bring in outside air that will distort the sensor reading.

JRCivic1

The problem is the heater circuit. Since you stated that you have changed out the O2 sensor, chances are good that BOTH heater circuits are not bad. This suggests that the problem is either a wiring problem or a blown fuse under the dash.
A crack or leak in the exhaust stream may cause faulty O2 sensor readings, but it doesn't affect the heater circuit. Also, if the code comes on right away... even before you crank the car or immediately after cranking, the issue is definitely not due to sensor readings, but picked up by either a brake or resistance in the circuit by the ECU.

kimbler99

thanks for the help but just got a chipped ecu and now got a code for tps I can't win


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