Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Steady check engine soon light ON

It happend during stady driving at low speed. Two troubles are idetified: PO328-knock sensor high input and Po456-EECS- emmision leak detected. I had tried a few times to clear the fault by disconnecting battery leads for 30 minutes, but when I start the engine, after connecting them back, the engine check light stays ON.

I checked hoses, the purge valve, the vent valve has resistance of 18 Ohms, and with key in run position ( engine stoped) I red 12 Volts on plug disconnected, and 0 Volts on connected back to it. I do not know conditions in which the readings suppose to be taken. I use high resitance electronic meter.

Some lights just require several drive cycles (driving long enough to get it fully warm.)

It seems like no one is willing to take a stab at this one. Perhaps because it might seem that the knock sensor is not related to the emissions leak detected system. I can’t figure out how they might be related either. But I’d start with checking to see if those two codes are set again after you turn off the CEL (have autozone or other aftermarket store do this for you) So if you in fact have both trouble codes, start with P0456. You have a tiny leak in your charcoal cannister/system. Do a good visual inepection as well as possible of all connections and valves and lines going to and from the cannister as well as the cannister itself. For P0328, you might try switching to a higher grade octane rating of gasoline, see if the helps. Other than that, I’d go buy a new knock sensor.

Resistance doesn’t mean something is working. You can maybe reset a defective computer by disconnecting it but maybe not a functioning OBD 2 setup. The light stays on because the problem is still there.

You CAN reset the computer with a scan tool. The prices on the Innova are even lower now. I saw one at Sears for around $80. When you reset the codes, the scan tool will flash all indicators until the drive cycle is completed. You can just disconnect it and drive the car without the drive cycle.

If the problem is still happening, you will get the check engine light again in a few trips on the road. Once the drive cycle is done, the computer will start to think normally again and will indicate that there is a problem.