After rereading step 4 on 11-81, if all is working correctly there shouln't be battery voltage between B19 and B20. I had ~3V which indicates the PCM is pulling pin B19 mostly to ground (I believe B19 is pulsing, thus 3V RMS on a meter).
Everything checks out ok.
I do not know where to go from here. There shouldn't be a code but it active shortly after resetting the code.
Any ideas at all?

 

As an additional test, I disconnected the A/F sensor (upstream) and immediately received the P1166 code. Then reconnected the A/F sensor.

Next I disconnected the O2 sensor (downstream) and immediately received the P0141 code.Then reconnected the O2 sensor.

Is there anyway to bypass or simulate the A/F sensor heater to satisfy the PCM and not generate the P1167 code? Wish I had the schematics/firmware code for the PCM to figure out what exact input or output (possible over current) is causing the PCM to generate the code. Would a code reader with real time data provide any insight to this information?

Totally frustrated and challenged!

 

A real time code reader might help you understand what's going on.

 

Page 11-15 shows your A/F sensor wiring to the PCM.

I think I'm reading the wiring diagram correctly. Pins C14 and C15 are for the sensor, while C13 and B19 control the heater circuit? Since the code is for the heater circuit malfunction, why are they having you test the sensor side of the circuit?

You may want to unplug the PCM and the A/F sensor and check that C13, C14, C15 and B19 are not shorted to ground at the PCM connector. Also check that those 4 pins aren't shorted to each other at the PCM.

Also, what is the OEM part number for the A/F sensor by using your VIN at the hondapartsnow.com site?

 

Hi PAHonda,
I agree with your circuit pinout for the sensor and heater circuit. BTW, it was my idea to test the sensor side of both the A/F and O2 sensors hoping for some indication of a problem. The codes generated by unplugging them were different which was encouraging.Nothing else learned here.

Great suggestion, I have tested those exact pins a couple of times. Testing for continuity end to end, testing for shorts between conductors/pins and testing for shorts to ground. All tests passed.

The OEM Part number for my VIN is 36531-PAA-306 which crosses to a Denso 234-9014. This is the sensor in the car.

What am I missing??? What else can I try? I'm thinking the sensors or the PCM's I have tried are defective but I don't know which one.

 

These are the ECM/PCM terminal pins. Backprobe the terminal B19 and terminal C13 to check the voltage readings with a fully warmed up engine.

 

In order to minimize any chance of error when back probing, the following voltage readings were measured between the CONTACT and chassis GROUND.
Contact C13 maintains battery voltage 14V (checked it several times after measuring B19).
Contact B19 is fluctuating between 2 -3 Volts to ground. As soon as the CEL illuminates, B19 goes to 14V. Reset the CEL and B19 voltage returns to 2-3V.
I reset the CEL a couple of time with the same results.

I let the car run for for another 5 minutes.
The CEL light was on. Both B19 and C13 measured 14V.
Reset the CEL, both B19 and C13 measured 14V. After a minute or two the CEL was back on. 14V at both contacts.
Did the step above twice with the same results.
The third time I reset the CEL it stayed off and both pins measured 14V (ie. 0V between the contacts).
Five minutes later, CEL remains off.
Every time the code was P1167.

 

Redbull - How is the signal measured in your attached tables? Testing in circuit like PLH is doing?

I think B19 should either be 0V to ground, or battery voltage to ground. That would either turn on or off the heater circuit.

I think a voltage drop test from B19 to the sensor connector with the key in the II position would help. Also C13 to the proper sensor. I think the CEL will have to remain off, key in the II position and not running, so there is current going through the wire.

 

PAhonda - The tables was not specific in how the signal is measured.


I found this article which seems to give good insight on diagnosing a recurrent heater circuit issue:

https://www.motor.com/magazine-summa...cuit-failures/

 

Here is some general troubleshooting info.