Siccished

I'm not sure if I found a mistake in the helm manual or a wires mismatched on my primary oxygen sensor connector.

Manual says: 12V between #3 & #4 BLK/YLW BLK/WHT
My car shows: 12V between #1 & #4... GRN/YLW & BLK/YLW


Has anybody else used helms manual to successful troubleshoot a heater circuit code? I ask because the next steps in the troubleshooting guide are to continue checking voltages using these pins and eventually replacing the ECU if they dont match. If mine are mismatched, or the helms manual doesnt have the correct pinout then im wasting time and money here..


O2 Sensor tested bad according to FSM method of checking resistance b/w 2 pins.
MY question is, when I clear codes via scanner the code will immediately come right back up within 5 seconds. When I've had other codes come up, i'd clear them and if they were valid they would return within 20 miles not a few seconds. I'm wondering if i have a wiring/ECM problem now..

Any insight?

Siccished

Just in case anybody ever searches for help.

Step 12 of trouble shoot FSM, verified i'm getting voltage to 02 connector BLK/YEL which comes from Fuse#6 ACG under hood.

B/C connector voltage is correct @ ECU.


FSM says to replace ECM... Oh great

Siccished

LOGGED troubleshooting in case anybody ever searches.. I will repost again when my replacement O2 comes in.

When i clear the codes via scan tool, the code immediately comes back on within 5 seconds. Not sure if it does this because the ECU immediately notices a faulty heater circuit OR if the o2 sensor is bad & it sees this right away? The answer to this will determine if i buy a new sensor or buy a used ECU along with keys to get passed immobilzer. Usually bad o2's would turn on a CEL after 20 miles right?





I have troubleshooted according to service manual in this sequence

-Check if O2 sensor is bad via resistance readings across heater circuit prongs- BAD
-Verify battery voltage across heater circuit readings @ o2 harness plug- NO
- Verify continuity from supplying power fuse to heater circuit prong @ harness- YES
-Verify voltage across ECU discconected plug 1 and connected plug 2. YES




From the first step the manual says to replace the O2 sensor, and from the result of the last steps the manual says to replace the ECU.

They go bad. Your first test result showed bad, resistance of the sensor heater circuit.

The PCM tests that circuit resistance first and if found to be bad it will not turn on the heater ground, so that's why there was no voltage on the test result you got.

Utests the heater circuit within the first 10 seconds after a start.

Same for most any circuits in most any of the other sensors, integrity of the circuit is tested right away. The performance of the sensor is checked/monitored after that.

Most other possible faults (activity related) of the O2 sensor take longer to show up.

Siccished

FIXED THIS!!!

-Bought replacement ECU
-Had the immobilzer board/chip swapped from my original ecu to the new donor ecu
-Old keys worked with this new ecu, as the immobilzer chip was programmed to my original key :-)
-O2 heater circuit CEL no longer on


Therefore, my old board's heater circuit was BAD.
Primary 02 sensor harness was only providing +12V, no ground. Apparently the ECU heater circuit switches ground to the harness and when the exhaust exhaust temp sensor reaches operating temperature, the ground is switched off because heater no longer needed.


Hope this helps somebody..
In my case, i had a friend that works with PCB boards resolder my immobilzer chips. Im sure a computer shop may be able to do this.