Hello, I've searched and my monitor problem seems a bit different from the others. All my monitors are ready except the O2 monitor. I've driven over 1000 miles, and I've recently tried to follow the GM drive cycle. Still no luck.

I recently did an LS conversion in my 1989 Toyota Land Cruiser. I have a Gen III 4.8 from a 2004 Silverado. All new cats and O2 sensors. No DTC. I've followed this drive cycle a couple of times with no luck:

1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
4. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
6. Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
7. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

It seems that the pertinent step is #4. And since all the other monitors have started, I'm guessing that there's something wrong with my 02 sensors, but how do I diagnose this?? Again, no DTC's.

Any insight? I can't get this past the California referee without this monitor starting.

Thanks!! - John

 

rig a VOM up and see if they're switching on and off. common problem is having the wrong o2 sensors for your harness (case grounded vs harness grounded)

also what software are you using to monitor them?

 

Doug, I'm not using any software. I'm getting a "Not Ready" with an Accutron OBD2 scanner. It's the only monitor labeled "Incomplete". I bought the Harness from Pacific Fabrication. They specified the O2 sensors I'm using.

Can you elaborate on what to test? The truck goes into closed loop mode so I assume the sensors are working properly, but then again I really don't have a very good understanding of how all this works.

 

if it goes into closed loop, then they are functioning and switching.

that it throws no codes also tells me they are functioning.

i would probably try more drive cycles on it, making sure not to disconnect the battery and clear the pcm

meanwhile you can look around here for a comparable schematic.

http://lt1swap.com/2000harness.htm


I am not familiar with that scanner, but before I had HP Tuners I used a $12 ELM 327 and the torque pro app for android to make sure my o2 sensors were working correctly.

 

I've looked at the lt1swap website, lots of great info. I'll keep trying to do the drive cycles more.

Can HP Tuners help diagnose? I was just starting to look into that. I have some tuning experience with Megasquirt on a 1970 BMW 2002 that I converted to FI, so maybe the learning curve won't be too steep for me.

 

Verify that you are going closed loop on your scan tool. Or see if your mv reading is staying at 450ish and not fluctuating. 450mv on a sensor means its inactive and that's the default reading. The reading should fluctuate between 0-999mv. Truck files typically will trim in open loop and go closed loop around 132 Degrees.

 

I have verified that I go into closed loop.