Hi guys, I have a 2001 ram 1500 4x4 with the 5.9l. The original cat plugged at 120k because this only had one cat for some reason, I also only have two o2 sensors (1 up and 1 down). I have since used the truck only for it to all of a sudden want to stall out (the only thing that gets it to go again is to push the pedal all the way to the floor and the truck takes off, then I hear the idle air control valve open all the way making a whistle and then a ton of rev hang ((1000rpm for 3-5 seconds like it's getting way too much gas)) then the cycle repeats). The truck will sometimes act normal and sometimes want to stall at every red light, and even loses power when driveing below 40mph (scary especially when towing). Over the past year I have spent time tracing wires and testing only for the oxygen sensors to keep popping my 20amp fuse for the heater circut. I have installed and tried 5 different sensors for the up and down only to find out the downstream is the main one at fault. 7 months into this journey I was able to make the system work for 5k mile when using an ntk upstream and a universal walker sensor for the downstream until the 20amp fuse blew again. I have 7 codes that normally show up (o2 1/1 heater circut high, heater circut low) (o2 1/2 heater circut high, heater circut low) (lambda sensor circut high). When I took the cat out i replaced it with a piece of straight pipe, and everything worked for a little while. I have no idea what's going on and why the system just up and stopped working. If anyone has any idea please help 🥲

 

You have a short in the heater circuit power feed somewhere. Might be up behind the engine, where things are fun too see.

You also have a large vacuum leak. That WILL give you performance issues....

 

That's the issue, is there a good way to find/test for a short? No other electrical system in the truck is broken/shorting out. The entire wiring harness from the fuse box and pcm to the trans area is completely untouched and has no visible issues. My speed sensor, shift mechanisms, 4wd accuator and everything all works perfectly fine. The sensors themselves will read and work but the heater system will fail causing the fuel trims to read absolute 0 and show nothing (when I had the walker universal the short trim would read +/-3%). When I install a new sensor the heater fuse doesn't blow right away, but when it blows it's a very audible pop and a bright light leaving nothing left of the metal inside.

Another interesting thing I've seen is people have issues when 55mph+ with bad o2 sensors, but this truck has no issues whatsoever going 90+ and holding in overdrive. The only strange thing is when going up a hill/applying decent throttle above 76mph (specifically) the air conditioning starts blowing out the defrosters, even if I have it turned off.

 

Gonna have to open up the harness, and physically inspect the wires for the heater circuits. So far as I know, that is the only thing they do, so, from the relay socket, down to the sensors. (might also try just swapping the relay... maybe its an internal problem there.....)

As for the vents.... That's normal. There is ALWAYS some air flow, and the vents stay in the position that is selected.... but, they are vacuum powered, so, if they lose vacuum, (large throttle openings....) they revert to the defrost. The condition is referred to as 'wild vents', there is a thread about that in the FAQ/DIY section.

 

Thanks very much for the fast feedback! I will inspect everything as close as possible and switch out the asd relay (or so I've heard that gives it's power). If all doesn't go well I'll report back here 😂

 

I think there is a separate relay for the O2 heater circuit..... ASD relay supplies power to several things, any one of which NOT working, would prevent the engine from running.

 

You need at least the 2 upstream O2 sensors. The 2 down stream are for the cat functioning and not for fuel management. Are there 2 O2 sensor wires dangleing with a connector at the end for the missing sensors? Is there an O2 bung on the missing side? Is it plugged off?

 

If his truck is federal emissions, there may only be two sensors.....

 

Never thought about that. Thanks for info.

 

I just inspected the entire harness and the plastic coating has done it's job and protected all the wiring and no wires are damaged from the outside of the fuse box and the pcm all the way to the sensor connectors. I also just ran a test by switching the asd relay and the horn relay and put a new 20amp o2 fuse in and let it warm up. The sensor system engaged and didn't pop the fuse, I'll report later if it does pop. Fuel trims do seem to be low and this happened the last time the sensors stopped working.