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Power loss - possible vacuum issue

Tiny
RYELANDO
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Okay great, I'll dig into this. It might take me about a week here because work is pulling me away for a few days but I will get this done!

And yes, to confirm the picture you sent, it did say Khz at the top of the screen so it would be 4000Hz.

One question before I start my research. When you say 'module', what exactly is that and where is it located? I'm sure I can figure it out when I start researching but thought I'd just ask to expedite the process. :)
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Thursday, August 19th, 2021 AT 10:30 PM
Tiny
KASEKENNY
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Okay. No Problem. We will be here. The module would be the PCM. I attached the info below for this. Basically the PCM sends 5 volts to the sensor and provides the ground.

So when you unplug the MAF sensor, you should have a steady 5 volts on the wire from the PCM for the 5 volt signal. Then ground on the other. Clearly the signal will not have anything as the sensor is what provides the signal back to the PCM on that circuit.

A quick test is if you have anything other then 4.8-5.2 volts on that 5 volt supply then the module is shorted.

I think we did that but these steps take you through that again and it is a good idea to check it.
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Friday, August 20th, 2021 AT 7:39 AM
Tiny
RYELANDO
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Perfect, thats great info. I understand now. I will get back to you once I can tackle this. Thanks so much.
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Friday, August 20th, 2021 AT 7:44 AM
Tiny
RYELANDO
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On step 16 of the test document you attached, it said to check for intermittent or poor connection at the module. I have accessed my module and it has 3 wiring connections full of wires going into it. How do we know which wire is coming from the MAF and what it should read where it connects to the module?
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Wednesday, September 1st, 2021 AT 11:17 PM
Tiny
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It is not so much inspecting the connection of the MAF but more checking the connector by wiggling it slightly. This will tell us if the code goes active that you have a connection issue.

However, I attached the wiring diagram for the MAF to the PCM. C3 is the one with all these connection in. Looks like it should be grey in color.
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Friday, September 3rd, 2021 AT 8:58 AM
Tiny
RYELANDO
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I did some more tests today.

First test: I ran the vehicle at idle and used the live scan tool to show the MAF readings in g/s and the DMM to show the Khz. I also wiggled some connections on both the MAF and PCM.

Second test: I did the same thing as the first test but applied some pressure to the gas pedal bringing it over 3,000 rpm's.

I did a full vehicle scan after the tests and it didn't show any new trouble codes other than the usual P0449.
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Friday, September 3rd, 2021 AT 12:32 PM
Tiny
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Yep. So based on that, it looks like the sensor is fine. I agree that the connections are not an issue.

The only thing that gives me pause is that the testing that you circled wants you to set up a generator so that you can take over the control of the sensor and make sure it reacts properly.

This is a dealer specific tool and not generally available. That is why your readings are not in that range however, they are acting correctly.

I say all this to say, if you are getting this code and the engine is demonstrating the issue that you have been seeing, you replaced the sensor already, confirmed the wiring is fine, then I would replace the module.
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Saturday, September 4th, 2021 AT 6:33 PM
Tiny
RYELANDO
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Okay, let's give that a shot. I found these guys online and will give them a try unless you can suggest a more preferable option:
https://www.flashmastersecm.com/products/2006-rendezvous-3-5l-engine-computer-12600928-programmed-to-your-vin-ecm-pcm
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Sunday, September 5th, 2021 AT 11:34 PM
Tiny
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Yep. I have not used them but know some who have. One did get a faulty ECM and they swapped it out with no issues so they seem easy to work with.
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Monday, September 6th, 2021 AT 6:41 AM
Tiny
RYELANDO
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My Module finally showed up today! I replaced it and relearned the keys for the ignition. The replacement works great, and the job went well. Although it didn't fix our issue.

It still gasps for air and sputters. I tried it on the highway twice in the last week (I have only been limping it down the block and back most days) and it was lacking in power so bad it ended up stalling out. It gasps and bucks really bad, it ended up kicking a p0300 code prior to stalling out. I still have the 0449 and 0171, although if I clear them all the only one that comes back is 0449. The 0171 and 0300 only show up if it try to push it a bit harder until it finally yells back at me, haha.

It did immediately start easily once I coasted to the side of the road and put it in park and turned the key.

So unfortunately, I don't think replacing the module solved our problem.
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Thursday, October 7th, 2021 AT 8:31 PM
Tiny
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Based on this info, I am clearly surprised that this didn't fix it. This means we are missing something and the fact that you have the EVAP code returning means we have an issue there that needs to be looked at.

However, a purge can definitely cause sputtering and stalling but the gasping doesn't match a purge valve issue.

Plus, this code is a circuit code so I still don't think that is the issue, but the PCM is telling us there is an issue.

So, let's run through this testing but I would start with pulling the purge valve and seeing if it looks like it is stuck.

The only way I can explain that this would be causing the issue is if the purge is stuck open and it is dumping fuel vapor causing the sputtering and the engine is gasping to try and even out the air fuel ratio.

Again, I have not seen this happen but that doesn't mean it is not possible.
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Saturday, October 9th, 2021 AT 6:32 AM

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