P0135 & 155 with P0118 & P0122
 

Hello, i have had the two O2 heater codes ever since I replaced them over a year ago. I have never had noticeable symptoms and have let them go.

Then I got the throttle position sensor code, its I believe its the low voltage P0122 code. I reset the OBD2 and have not driven it.

I noticed that the heater doesn't get warm and found that code p0118.

I did some minor multi meter test on the TPS. I checked for votage and checked that the sensor was registering mechanically.

I crossed referenced the Coolant Temp Sensor with the dash gauge and they both read the same temp. I pulled the connector out and the truck wouldn't start.

I have not done any test on the O2 sensors.

I have an 02 LS 4.3 model Blazer. The engine takes a few minutes to idle down from 1500 rpm to around 1000. Once I am on the road it maintains 600 - 700 rpms which is a little higher than norm. The normal operation temp has always been under 200.

I have no other issues as stated. Oh yeah and I also temperature difference before and after the cat to check blockage. It was within 40 degrees different I think. But Torque Pro always states "Incomplete" for Catalyst, Evaporative Sys and O2 sensor but "Complete" for O2 Heater Sensor.

Thats all the information I can think to include. And thanks in advance, I have met some very impressive people on this forum. I have never had to look elsewhere.

Zell

First some basics about sensor codes. The engine computer is getting a signal level that is out of bounds. This is usually because:

1. The sensor is faulty
2. The reference voltage or conditioned ground is faulty
3. The wiring between the sensor and the Engine computer is faulty
4. There is a more general voltage or ground problem somewhere
5. The variable being measured is actually out of bounds and the reading is accurate
6. The engine computer is bad (almost never true)

• What O2 sensor codes do you get? There is the heater circuit and there is the actual sensor output waveform. Can you graph O2 sensors?
• The best test for a bad cat is the rear sensor graph and a back pressure test at an O2 sensor port. The shade tree diagnostic is remove the O2 sensors and see if it runs better
• What coolant temp does live data in your scanner report?
• On the TPS, measure the reference voltage relative to the TPS conditioned ground (blk/gry). Then look on your scanner with key on engine off and observe that the TPS changes smoothly with expected results through the full position sweep.
• Be sure that your coolant circuit is fully bled. Nose up, revved up slightly, best is the bleeding funnel in the neck filler, heater on, feel both hoses. If still no heat, flush the core with garden hose pressure (not full nuke mode), both directions.

George

Thank you sir. I will check each as directed and will check back.