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Discussion Starter #1 (Edited)
Hey guys, hope you're having a better week than mine because I have been in and out of the dealership several times going absolutely banana's over my car. Last week I had a check-engine light come on for the first time in about 5500 miles. Checked the error code on the diagnostics menu and it read "P1621". Checked other online sources and found out it's a powertrain issue but where/what exactly not sure. I kept driving it for a shortwhile just to test it out and the gear-shifts felt off, as if not enough gas or oil was being pressured, especially on 3rd and 4th gear shifts, the car hopped and stuttered so I had to literally pull over and shut it off. Had it towed to the dealership immediately in the middle of the night! Spoke to the dealership next day and they said it's your Oxygen sensor that's been acting up; but they did not replace the part, they told me they won't so they make sure the electrical/computer is functioning and not giving wrong readings because the car is pretty much brand new so all they did was a "major software update". Got my car back, no more check-engine light, it did a little better on the gear shifts than before and no more drop in pressure or throttle response. But, the next day all the symptoms came back again and Bam! Check-engine light, same error code and this time the car almost stalled in the middle of an afternoon rush-hour traffic, I had to pretty much hammer the gas pedal to keep it from turning off but it wasn't worth it did not wanna damage it any further... so I pulled over and literally had to get down and push a 4400 lbs dead weight to the emergency lane where it was wide enough to not cause any traffic jam. Had the car towed... yeah I wasn't having the greatest of days...

This time I went nuts at the dealership and spoke to the service manager, tried to keep my cool but I emphasized how they could have replaced the part the first time after keeping it for a full 24 hours. Well that's that, I made sure they'll replace the Oxygen sensor, do a test drive, it's been with them for three days now and it's going through electrical procedure as we speak. Has anyone experienced similar issue(s) thus far or this exact error code before? What could cause it? I really look after my car and serviced it twice since I bought it... ugh :(
 

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Does the HC warranty cover towing bills? I think I for one would look for another dealership to do my work.
 

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Discussion Starter #3
Does the HC warranty cover towing bills? I think I for one would look for another dealership to do my work.
Yes they covered the towing bills and all Mopar parts are under warranty, I invested quite an amount in insurance for this *****. But you'll laugh at me if I tell you this: in our country we only have one dealership for Dodge, Chrysler, Jeep and Ram. It's a really tiny country in the Middle East it's a monopoly pretty much there so is no way another dealership can just walk in and do business here lol :D The only other way you can purchase a Chrysler or a Dodge is through these "ordering offices" what we call 'em and they order a vehicle for you, ship it but then once you receive it you'll have to register it with the dealership so you can get it serviced later. But it's an available method either way in case you don't find the exact options you like at the dealership.
 

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Anything that affects the O2 sensor 2.5V bias will set this code. This can be any 1 of four O2 sensors as well as a short to ground on K902 or K904 circuits. It's not as simple as "replace the oxygen sensor".

Good luck.






P1621-O2 SENSOR REFERENCE VOLTAGE CIRCUIT LOW


Theory of Operation



Normally, the O2 Sensor signal voltage will fluctuate between 0.0 and 1.0 volts. On rare occasions, the signal voltage can drop below 0.0 volts. The Powertrain Control Module (PCM) is not able to calculate a negative voltage from the O2 Sensors. To prevent this, a 5-Volt reference voltage is pulled through a pull up resistor on the O2 Sensor Return circuit (ground path) for the O2 Sensors. This provides the 2.5 volt bias voltage on the O2 Sensor Return circuit and allows the O2 Sensor signal voltage to shift to the 2.5 - 3.5 switching voltage range for the O2 Sensor.




    • On vehicle/engine combinations that use only the traditional switching O2 Sensors, both of the Upstream and Downstream O2 Sensor Return circuits originate from a single source within the PCM. Because of this, a short anywhere in the wiring in any of the O2 Sensor Return circuits will affect all of the Upstream and Downstream O2 Sensors.
    • On vehicle/engine combinations that have wide-band Upstream O2 Sensors and switching Downstream O2 Sensors, the Upstream and Downstream O2 Sensor Return circuits are separate within the PCM. In this case a short anywhere in the wiring in the Downstream O2 Sensors Return circuit will only affect the Downstream O2 Sensors. The PCM performs individual diagnostics on the O2 Sensors Return circuit for each wide-band Upstream O2 Sensor.
When Monitored and Set Conditions
When Monitored: This diagnostic runs continuously when the following conditions are met:




    • Battery voltage between 11.0 and 15.75 volts.
    • With the engine running.

Set Conditions:




    • The Oxygen Sensor return circuit voltage for the O2 Sensors is below a calibrated threshold for 60 seconds.

Default Actions:




    • The MIL light will illuminate.
Possible Causes:
O2 SENSOR RETURN CIRCUIT SHORTED TO GROUND
O2 SENSOR
POWERTRAIN CONTROL MODULE (PCM)



 

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Discussion Starter #5
Anything that affects the O2 sensor 2.5V bias will set this code. This can be any 1 of four O2 sensors as well as a short to ground on K902 or K904 circuits. It's not as simple as "replace the oxygen sensor".

Good luck.






P1621-O2 SENSOR REFERENCE VOLTAGE CIRCUIT LOW


Theory of Operation



Normally, the O2 Sensor signal voltage will fluctuate between 0.0 and 1.0 volts. On rare occasions, the signal voltage can drop below 0.0 volts. The Powertrain Control Module (PCM) is not able to calculate a negative voltage from the O2 Sensors. To prevent this, a 5-Volt reference voltage is pulled through a pull up resistor on the O2 Sensor Return circuit (ground path) for the O2 Sensors. This provides the 2.5 volt bias voltage on the O2 Sensor Return circuit and allows the O2 Sensor signal voltage to shift to the 2.5 - 3.5 switching voltage range for the O2 Sensor.




    • On vehicle/engine combinations that use only the traditional switching O2 Sensors, both of the Upstream and Downstream O2 Sensor Return circuits originate from a single source within the PCM. Because of this, a short anywhere in the wiring in any of the O2 Sensor Return circuits will affect all of the Upstream and Downstream O2 Sensors.
    • On vehicle/engine combinations that have wide-band Upstream O2 Sensors and switching Downstream O2 Sensors, the Upstream and Downstream O2 Sensor Return circuits are separate within the PCM. In this case a short anywhere in the wiring in the Downstream O2 Sensors Return circuit will only affect the Downstream O2 Sensors. The PCM performs individual diagnostics on the O2 Sensors Return circuit for each wide-band Upstream O2 Sensor.
When Monitored and Set Conditions
When Monitored: This diagnostic runs continuously when the following conditions are met:




    • Battery voltage between 11.0 and 15.75 volts.
    • With the engine running.

Set Conditions:




    • The Oxygen Sensor return circuit voltage for the O2 Sensors is below a calibrated threshold for 60 seconds.

Default Actions:




    • The MIL light will illuminate.
Possible Causes:
O2 SENSOR RETURN CIRCUIT SHORTED TO GROUND
O2 SENSOR
POWERTRAIN CONTROL MODULE (PCM)


Thanks a lot! This was really informative. But what are like the physical causes that could trigger the sensor circuit to act up or drop? I mean could it be some early on spirited driving or burnouts for example?
 

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Thanks a lot! This was really informative. But what are like the physical causes that could trigger the sensor circuit to act up or drop? I mean could it be some early on spirited driving or burnouts for example?
The way you drive should not cause this circuit fault. This DTC is caused by a short to ground on K902 or K904 circuits. This can be in any of the four O2 sensors, the associated wiring harness or PCM internal fault.
 

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Discussion Starter #7
The way you drive should not cause this circuit fault. This DTC is caused by a short to ground on K902 or K904 circuits. This can be in any of the four O2 sensors, the associated wiring harness or PCM internal fault.
I see alright man thanks a lot. I just received from dealership they need to replace the whole control module and redo wiring. Ordered the parts and hopefully they'll be available soon so I can get my baby back :(
 
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UPDATE: Parts have just arrived should be fitted on the car by tomorrow or maximum the day after and then it's test-driven, it's been with the dealership for almost two weeks now. The wait is long but it's worth it! As long as I get it back a hundred percent. I'll tell y'all about the part details when I receive more information.
 

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UPDATE: Parts have just arrived should be fitted on the car by tomorrow or maximum the day after and then it's test-driven, it's been with the dealership for almost two weeks now. The wait is long but it's worth it! As long as I get it back a hundred percent. I'll tell y'all about the part details when I receive more information.
Good luck with everything bro.
 
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Discussion Starter #10

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UPDATE: More bad news... after they replaced the PCM earlier and did the test drive today another check-engine light popped up this time it had to do with the Oxygen sensor itself. Two of them were acting up. Thankfully parts are available locally and there won't be a need for ordering, I was told so after dealership managed to calm me down with tea and chocolates :D. Car should be finished during the weekend (They'll be working overtime hours just for me, oh I feel so special :D) It's been nearly a month I haven;t driven anything over a 100 bhp's :( currently driving my sister's old Honda civic while hiding as much dignity as I have left behind a pair of Police sunglasses :D
 

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UPDATE: I haven;t driven anything over a 100 bhp's :( currently driving my sister's old Honda civic while hiding as much dignity as I have left behind a pair of Police sunglasses :D
After a month in a Honda, I bet those are some pretty small sunglasses.
 

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Discussion Starter #13
UPDATE: Finally got my car back yesterday! :) Total parts replaced:

- PCM (Powertrain control module) replaced and wiring redone.
- 2 out of 4 O2 sensors replaced.

Car feels a lot smoother in gear shifts especially on low-end RPMs. It seems to be "breathing" a lot better just sounds a lot more healthy than before! Glad to have the old girl back! :D
 
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UPDATE: Finally got my car back yesterday! :) Total parts replaced:

- PCM (Powertrain control module) replaced and wiring redone.
- 2 out of 4 O2 sensors replaced.

Car feels a lot smoother in gear shifts especially on low-end RPMs. It seems to be "breathing" a lot better just sounds a lot more healthy than before! Glad to have the old girl back! :D
Hi
Where r u from and could i know which oxygen sensore replaced ?
Upstream or downstream?
 

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Discussion Starter #15
Hi
Where r u from and could i know which oxygen sensore replaced ?
Upstream or downstream?
Hey, I'm from Kuwait and I don't know if you've come across this post it was above it has detailed info about my issue:

P1621-O2 SENSOR REFERENCE VOLTAGE CIRCUIT LOW

Theory of Operation


Normally, the O2 Sensor signal voltage will fluctuate between 0.0 and 1.0 volts. On rare occasions, the signal voltage can drop below 0.0 volts. The Powertrain Control Module (PCM) is not able to calculate a negative voltage from the O2 Sensors. To prevent this, a 5-Volt reference voltage is pulled through a pull up resistor on the O2 Sensor Return circuit (ground path) for the O2 Sensors. This provides the 2.5 volt bias voltage on the O2 Sensor Return circuit and allows the O2 Sensor signal voltage to shift to the 2.5 - 3.5 switching voltage range for the O2 Sensor.




    • On vehicle/engine combinations that use only the traditional switching O2 Sensors, both of the Upstream and Downstream O2 Sensor Return circuits originate from a single source within the PCM. Because of this, a short anywhere in the wiring in any of the O2 Sensor Return circuits will affect all of the Upstream and Downstream O2 Sensors.
    • On vehicle/engine combinations that have wide-band Upstream O2 Sensors and switching Downstream O2 Sensors, the Upstream and Downstream O2 Sensor Return circuits are separate within the PCM. In this case a short anywhere in the wiring in the Downstream O2 Sensors Return circuit will only affect the Downstream O2 Sensors. The PCM performs individual diagnostics on the O2 Sensors Return circuit for each wide-band Upstream O2 Sensor.
When Monitored and Set Conditions
When Monitored: This diagnostic runs continuously when the following conditions are met:




    • Battery voltage between 11.0 and 15.75 volts.
    • With the engine running.

Set Conditions:




    • The Oxygen Sensor return circuit voltage for the O2 Sensors is below a calibrated threshold for 60 seconds.

Default Actions:




    • The MIL light will illuminate.
Possible Causes:
O2 SENSOR RETURN CIRCUIT SHORTED TO GROUND
O2 SENSOR
POWERTRAIN CONTROL MODULE (PCM)
 

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Thanks for this post. I have seen a lot of o2 sensor type issues with this car, I wonder why the sensors go out so fast... That's strange. Mine is going in the shop for some type of related issue tomorrow. Only had the car for like 3 days. But man I do love driving this thing. Been driving with the black key just so when I drive with the red key I'll feel that new car feeling again hehe, but I'm still breaking her in.
 
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