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Amedee
Amedee, Dodge Technician
Category: Dodge
Satisfied Customers: 21841
Experience:  ASE Master Technician advanced level specialist. Wisconsin certified emissions state inspector
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Dodge Stratus SXT DTC P0491

Resolved Question:

Chris, I fixed the leaking trans cooler line. It had leaked down the harness under it which runs over to the air pump/MAF sensor. I unwrapped the plastic tubing around the harness and cleaned everything real good. I also disconnected the the bottom connection (see image either c170 or c171 - whichever is bottom when looking from front of car down under intake plenum)

because it was saturated w/ trans fluid from the leak. I erased the DTC P0491. It came back a couple of starts later and has stayed on. Do you have any tips to find out what's causing this DTC?

Here's an exploded view
Submitted: 3 years ago.
Category: Dodge
Expert:  Amedee replied 3 years ago.
Hello!

Did you still need help?

Are you looking for a particular expert?
Customer: replied 3 years ago.
Chris had helped me recently but if you have the answer I still need help.
Expert:  Amedee replied 3 years ago.
I can certainly help you if you would like..or if you would like to wait for chris to come on line, I can send him this link..
Customer: replied 3 years ago.
I'll take your help.
Expert:  Amedee replied 3 years ago.
Did you say that the air pump was full of fluid?
Customer: replied 3 years ago.
I haven't pulled the pump off yet. The harness was covered with transmission fluid up to the connector (see my first post). I cleaned w/ electronic spray cleaner. I haven't done any electrical tests as I don't have a DRBIII to actuate the ASD relay or a Miller #8815 to probe the PCM harness connectors. Do you know of any work arounds without these 2 special tools? Or any other tricks that might help diagnose P0491?
Expert:  Amedee replied 3 years ago.
Well, I can tell you that 9 times out of 10, the air pump is the root cause of this code. I would start by visually inspecting the air injection pump hoses, tubes, and inlet filter. If the air pump is ok, then sometimes the air pump relay is the root cause. Check the air pump for power. Also, sometimes the mass air flow sensor or circuit can trick the computer is setting this code. If you had access to a scanner, you could run the air injection pump using the Actuator Tests. If the pump runs, the pump motor and Powertrain Control Module re functioning properly and the Mass Air Flow Sensor needs to be tested for the air injection system. You can disconnect the MAF, and monitor the ASD feed wire to the MAF, with a test light, it should light brightly. If you were to disconnect the mass air flow sensor, the MAF voltage should be near 5 volts. If you jump the sensor signal wire to the sensor ground and the voltage should drop to 0 volts.
Customer: replied 3 years ago.
I wasn't able to try anything to late last night. I unplugged the 2 pin connector that goes into the air pump. I put a test light on the power wire from the relay. With key on I get nothing. A few seconds after ignition the test light came on. Does this mean everything is good up to the air pump? How do I turn on the pump without the DRB? Or is there an alternative to the DRB?
Expert:  Amedee replied 3 years ago.
Hello!

Any scan tool including the DRB3 will be able to run the actuator test mode which will run the pump. If you do not have access to any sort of scanner, then you can try to power it up by running a wire straight from the battery right to the pump. However, this way you are by passing the entire power circuit.
Customer: replied 3 years ago.
Any recommendations for a scanner would be helpful -- I've spent quite a while looking. All I am finding is code readers and some that graph sensor data.
Expert:  Amedee replied 3 years ago.
I can sure recommend some... but they are a bit pricey..
Customer: replied 3 years ago.
OK, I will need to figure it out without a scanner then. Thank you for your patience ... I don't do this stuff everyday so I need things explained in a little more detail. What is the safe way to bench test the air pump? I have it removed. I have a multimeter. Can you explain in detail how to connect directly to the battery? I think the guage of the wire used matters right? Should there be a fuse on the positive side? 40A fuse?
Do I have this right?
Pump power pin to Battery Positive
Pump ground pin to Battery Negative (or Chasis Ground)
Expert:  Amedee replied 3 years ago.
YES.. that is correct. But you have to check to see which wire on the connector is power and which one is ground. From there, you will know what pin on the pump needs to get power and ground. Do not confused the two or you could burn out the pump.

YES.. use the same gauge wire on the vehicle. You do not have to use a fuse, but just be careful not to touch the hot wire to any ground while doing this.

Just supply power and ground to the air pump (the correct pins) and the pump should run.
Expert:  Amedee replied 3 years ago.
YES.. that is correct. But you have to check to see which wire on the connector is power and which one is ground. From there, you will know what pin on the pump needs to get power and ground. Do not confused the two or you could burn out the pump.

YES.. use the same gauge wire on the vehicle. You do not have to use a fuse, but just be careful not to touch the hot wire to any ground while doing this.

Just supply power and ground to the air pump (the correct pins) and the pump should run.



Customer: replied 3 years ago.
From the connector pin-outs is the guage the number before the color? 10TN = 10 guage Tan wire?
Ground: From pump to ground the guage goes 10, 16, 10, 16
Power: From pump to power distribution center the guage goes: 10, 10, 10, 14
Is the 10 guage wire what I should use for both?
Expert:  Amedee replied 3 years ago.
YES.. you will be able to use a 10 gauge wire no problem. Remember, you are only going to run it for a few seconds... just long enough to see if the pump runs.. no longer.

I am not sure about the gauge number on the diagrams. I have been reading wiring diagrams for years and have never needed to know this. Just use the biggest wire... one that is as big as one that is being used in the system, and you will be ok.
Amedee, Dodge Technician
Category: Dodge
Satisfied Customers: 21841
Experience: ASE Master Technician advanced level specialist. Wisconsin certified emissions state inspector
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