First off, thanks if you are reading this and hoping to help. I'm hoping to save $150/hr that I will pay just to have my problem diagnosed...led alone fixed, if you can't help me.

Somewhat quick summary before problem listed below.
'99 D2 bought 2 years ago, 105k miles.
All major service has been done since purchase, all new fluids, new head gaskets too.

Problem: codes P0134 & P0154 (front O2's NO ACTIVITY) and so the truck is running in OPEN LOOP constantly, burning more gas than usual.
What I've done to date:
-replaced the O2 sensors thrice with Atlantic British O2's and then BP of Utah front O2's. I would say it isn't the sensors at this point.
-w/ multimeter, checked that the O2 plugs (connectors) were receiving power, they are.
-w/ multimeter, checked that the other three wires in the connector had clear flow of info TO the ECM, checked out. (doing pin-outs is fun...or not)

It seems that the sensors are good, they are getting power, and the wiring between the sensors and the ECM is good.

So, what else can I check? Is my ECM bad? Can an electrical guru with the right equipment fix/repair the ECM and the communication with the sensors? Or will this just inevitably lead me to buying a new/used ECM and getting it flashed to my truck?

Thanks in advance, DIIB.

 

Whelp.....

I've never seen an ecu go bad in a disco...

Do this, Try reading the ECU oxygen sensor input with an OBD scanner, see if you have any activity.

If its 0, check the voltage while the sensors are plugged into the ecu. If you have voltage, I would suspect ecu.

If volts are stuck at .8 or stuck somewhere like .999 on the OBD scanner, you have voltage (most likely from the heater circuit) bleeding into your signal line. Pull fuse #2 in the engine fuse box and see if your voltage drops down.

 

Thanks for the help and reminder.

I DID hook up a scanner and watched LIVE after installing new O2's set #2 and #3, and I think I remember seeing some movement initially about the heater circuit, but my voltage was stuck at the default position (think it's .45 if I remember right) and didn't budge, ie NO ACTIVITY - and stays in open loop.

I'm just now re-hashing what all I did, and attacking this problem again. I believe my current set of O2's were the orange connector LR's from British Parts of Utah.

I will try what you suggested, hopefully soon, and get back with results.