Hello again, 1999 ram 2500 v10 owner here, again. So, I changed all 4 of my O2 sensors, was getting a high voltage code for bank 1, sensor. Checked, bad wires, fixed, no more code. Shortly after that, I began getting a code for bank 2, sensor 1. Checked, looked, stared and I don’t see anything visually wrong with the wiring. Swapped that o2 with bank 1, sensor 1 to see if it was the sensor. No readings on bank 1 and bank 2 is still high. I assume that the sensor Is no good anymore and the wiring to the sensor plug (truck side) is faulty too. Rigged up a harness with long leads to the plug to check continuity to the PCM. With key off I got continuity on a few contacts with 3 of the 4 wires. The black wire has nothing. My question is am I going about this the right way, diagnostically? Should there be continuity with the key off or only with the key on? Does not having continuity mean that there’s a break in that wire? Does it mean anything at all? Does this make sense? Thanx guys, Lynn.

 

Not sure if I'm reading this right. Did you remove the connector on the PCM and check between the PCM connector and the individual O2 sensor connectors ? If so that would be a good way to do check the wiring. (However you would not need ignition on for this.) Pin 4 on connector C1 at the PCM is the sensor ground for all 4 sensors. The individual sensors are on pin 24, 25, 26, 29. (Note the 98 FSM appears to have an error as it lists pin 29 twice so these are from the 01 FSM).

If you get continuity on 3 of the pins from each O2 connector to the PCM that's good. The fourth gets power for the heaters from the PDC.

 

Yes, that’s exactly what I did. Thank you for your reply. Can you tell me how to check the black wire please? I was really hoping there was a break in that wire because if not I don’t have a clue what could be causing the code. Lynn.

 

The FSM doesn't show a solid black wire but the newer O2 sensor might have them. Assuming these are the 12V supplies for the heaters they go to fuse K in the PDC. They get power via the auto shutdown relay which isn't on when the engine isn't running so it's probably easiest to check continuity to the fuse.

 

That sounds easy enough. Thank you again for your help. The wires like black with a white stripe, possibly a dark blue. Anyways, if there’s no continuity that’s easy enough to fix. Any advice on what I should do if the wires good? I’ve checked the wires and made sure they weren’t laying on the tranny or exhaust....I shoulda never messed with them. Thanks again, Lynn

 

What code #?

 

Black/white stripe is the ground for the heaters. Where they go is a bit of a mystery on a 99.... In the 98 FSM they just connect to ground at G105 at the front of the engine. In 2001 the upstream O2 sensor heaters are controlled by the PCM and the pre/post cat ones are not. I don't know when the change was made.

As Moparite wrote, what are the exact codes for which sensor ?

 

I don’t remember the number but it was bank 2, sensor 1 high voltage

 

That typically means that 12V heater voltage bleeds onto the sensor signal. Could be the sensor itself or some wiring issue. You already swapped left and right and it didn't change correct ?

 

Yes, I swapped them. I went ahead and bought another sensor and threw it in. Immediately threw a code for bank 1 sensor 1, replaced sensor that and so far no codes but now my engine is surging for some reason. And on my obd2 scanner I keep getting reading for 5 sensors, not 4. Idk. All the sensors are switching back and forth but bank 1 sensors 2 and 3 are steady at 99.2v for some reason but the fuel trims are dynamic. Lynn