Hi everybody,

I have a '98 EB, 5.4, 4x4 with 49,000 miles. I've had this truck since new and have never had any problems.. until now. Yesterday I started the truck cold and the check engine light came on after a minute or two of driving. The light stayed on during the 15 minute trip, and on the return trip home. The truck ran fine the whole time. I disconnected the battery when I arrived home, and reconnected about 20 minutes later. I started the truck and the light was off, so I went for a 15 minute drive and all was well, no light, running great. This morning on the way to work (after about 2 minutes) the light came back on again, still running fine. I do realize that could indicate almost anything sensor realted, but I was just curious if there was common issue that has shown up over the years. As scary as it is, I'm going to the local Auto Zone after work, they offer free diagnostic readings. I'll post the codes once I have them.

Thanks,Duane

 

UPDATE! - I had a scan at the local Auto Zone and came back with a P0156 code. The parts guy thought that was the passenger side O2 sensor closest to the exhaust manifold. I don't have a set of shop manuals, can anybody confirm? I have also heard about a TSB in regards to the A/C condensate dripping on this particular sensor. Does it only ruin the sensor or does it damage something in the wiring harness?

Thanks, Duane

 

This is straight from the manual for 98 Expy, if looks like it is a problem with the circuit (wiring). I don't have any updates, sorry.
The DTCs associated with HO2S signal circuit malfunction are DTCs P0131, P0136, P0151 and P0156. The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt. The HO2S Monitor evaluates both the upstream (fuel control) and downstream (Catalyst Monitor) HO2S for proper function.

2. Once the HO2S Monitor is enabled, the upstream HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage. A fixed frequency closed loop fuel control routine is executed and the upstream HO2S voltage amplitude and output response frequency are observed. A sample of the upstream HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate. A HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the Output State Monitor (OSM) and by measuring the current going through the heater circuit. The HO2S Monitor DTCs can be categorized as follows:

The DTCs associated with HO2S lack of switching are DTCs P1130, P1131, P1132, P1150, P1151 and P1152.

The DTCs associated with HO2S slow response rate are DTCs P0133 and P0153.

The DTCs associated with HO2S signal circuit malfunction are DTCs P0131, P0136, P0151 and P0156.

The DTCs associated with a HO2S heater circuit malfunction are DTCs P0135, P0141, P0155 and P0161.

The DTC associated with the downstream HO2S not running in on-demand is DTC P1127.

The DTCs associated with swapped HO2S connectors are DTCs P1128 and P1129.
Good luck. Chuck

 

Dave Powell
Hey, thanks for the info. I have a o2 sensor problem i am working on. I have a problem with the heater circut side of the sensor. when you clear the code all is well, as long as the truck stays hot. Let it cool down a little and within a mile or so the check engine light pops on. You can clear the code and drive with no problem, but dont let the truck set parked for long or the light will come on. I think i have a computer problem. I dont have the service book at this time, any recomendations. Dave

 

I had my O2 problem taken care of today. Turns out the AutoZone guy was wrong, it was the drivers side after the cat. New O2 and all is well.