[rkresse]

Honda civic 98 has po131 code low voltage at primary o2 sensor can't get 12 v to heater getting very weak ground signal from ecu. Could this be grounding problem?

[TxGreaseMonkey]

Not likely. You probably need to replace the sensor:

https://www.askmehelpdesk.com/cars-t...tml#post223376

[rkresse]

Sensor is new not getting 12v to the sensor heater thanks rick

[TxGreaseMonkey]

. Clean the main ECM ground, located on the thermostat housing, with abrasive cloth.

. Perform K-Test on the ECM:

The K-Test: Remove the MAP Sensor connector and turn the ignition switch to ON (Position II). Using a multimeter, check for 5 volts going between the MAP Sensor connector's reference wire (+) and ground. As you look at the connector, this is the socket on the right. Really press the black test lead into a cleaned main ECM ground on the thermostat housing. If the voltage is low, it's probably indicating ECM failure. Most failed ECMs will record a fraction of a volt. To me, the K-Test is simple, elegant, and accurate.

The ECM (computer) is nothing more than a “power transistor,” whose job is to supply the proper voltage to a host of sensors, under constantly varying conditions. There's a real possibility the ECM is failing, if it's not providing the proper reference voltage to the Heated Oxygen Sensor. Try substituting a known good ECM.

. Check for poor connections or loose wires at the shock tower and the ECM.

I suspect the ECM is failing.

[rkresse]

HI, cleaned ground wire,k-test shows .1 volt bought ecu on eBay
Will let you know thanks Rick

[TxGreaseMonkey]

Yes, the ECM is fried. Here's how to swap it out:

https://www.askmehelpdesk.com/cars-t...tml#post235038

[rkresse]

Ecm took care of problem. Ready for smog test when get the drive cycle done thanks rick

[rkresse]

Wow now have ck engine light no codes, good alt fuse,new ecm tested ignition switch unpugged all sensor in position 2 unreal..
Load ak go to desert lol