2015 Jeep Grand Cherokee P1621

Joseph Technician South Carolina Posted   Latest  
2015 Jeep Grand Cherokee Limited 3.6L (G ERB) 8-spd

Hey Everyone I know the rules, and I hate to be this guy but I hope someone might be able to help me out.

This Jeep is setting a p1621 oxygen sensor reference low pretty much right after startup after replacing the passenger side cylinder head for a misfire issue. 

I pulled some quick data and all sensors are switching between 0-1 when they should be 2.5 to 3.5 so I know it's not a shorted sensor but a short outside of it.

Visual/shakedown of all the harnesses and all are back in their original places and nothing looks out of the ordinary

Again a hate to ask if anyone has btdt or a silver bullet on if there is any places this circuit likes to short out before I start taking things back apart, and of course I am under the gun, but I figure everyone gets one every once in a while lol.

Thank you for anyone for their suggestions and their time

Lazer Mobile Technician
New Jersey

You need OEM Sensors, make sure its not an aftermarket.

Ð Awarded
Stephen Owner/Technician

Check the wiring diagram, and see what wires are high and low for the sensors at their plug. Then get a test light to battery positive and the other to the high terminal, then the low. Watch your graphing pid when you do it. See that the graph responds. If it does the wiring is good and you have an issue with the sensors.

Ð Awarded
Jordan Diagnostician

If the “return” circuit is shorted to ground on any of the 4 sensors this will occur to all of them.

Ð Awarded
Richard Technician
New York

I had never seen this code before so I went to alldata to read up on it real quick and it mentions that the sensors should be switching between 2.5 and 3.5 volts. if they are shorted they will be less than 1 volt. It than suggests going around and disconnecting the sensors one at a time until the voltages go to where they are supposed to be. Good luck with it and let us know what you find.

Ð Awarded
Robert Technician

Not related if not flagged on Mitchell but Dodge used to pop them codes P1621 or P1622 back … while h02s were working normal or after new sensors needed a PCM reflash on 3.6 then expanded to 5.7 .

Ð Awarded
Joseph Technician
South Carolina

Robert, Thanks I saw that tsb but it didn't list the jeep's in there so I was trying other avenues first but now I have believe I exhausted all other avenues and might give it a shot just to see what it does. According to the dealer where it was they had flashed it for a recall but witech is still showing it out of date. Thanks for the info and I will let you know.

Ð Awarded
Caleb Diagnostician

There should be 2.5 volts on the ground side of the sensing portion of the 02 sensor. Takes 5 minutes to check with a meter or scope.

Ð Awarded