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Quaraxkad

L67 Swap PCM issue

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My Cutlass build has been stalled for about a month, due to this PCM issue. To summarize: I have an L67, 4t65e-HD, and PCM from a 2004 Impala SS. The car will start and run for a second or two before the engine stops. This sounds like a VATS issue, although I have tried every possible setting to disable VATS in TunerCATS. I have tweaked VATS in TunerCATS over and over and over, and even bricked a few PCM's when the WinFlash software crashes during a write. I have tried every setting and combination of settings I can think of. No matter what I set for VATS, the result is the same. It cranks, starts up, then shuts off after a couple seconds. To complicate things, I also have a 2000 GTP PCM. With that installed, the car starts and runs just fine! So I am pretty confident my wiring is good. I have fuel, I have air, I have spark. I can't just use the GTP PCM or it won't shift properly due to differences in the transmissions between those two years. Same story with a 1998 Lumina LTZ PCM. It starts and runs, but it's programmed for N/A and also can't operate the transmission properly.

I have compared the pinouts for my 1998 Lumina LTZ wiring harness and the 04 Impala PCM. There *are* some differences, but none of them appear to be important. For example, the Impala PCM has multiple pins that act as grounds for various sensors (C1-12, C1-13, etc), while the Lumina grounds all those sensors through one pin (C1-17). The Impala has a 5v reference output on C1-10 dedicated to the MAP sensor, on the Lumina that is shared with other sensors on C2-33. There are also two additional power wires on the Impala PCM. C2-24 needs power at ON and START. C2-23 needs power only at START, during cranking. I have tried hooking up both of these and confirmed that C2-24 is required to turn on the PCM, but C2-23 doesn't appear to do anything. (Before I learned about C2-24, the engine would crank and fire *one* cylinder but never start up.)

pcm_comparison.jpg

Anybody have any ideas?

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I'm no expert when it comes to aftermarket tuning but your displayed schematics have a minor difference, the Lumina wiring harness is not quite the same when it comes to the signal for the oil pressure switch. If the PCM is not getting the signal then the PCM will shut down the engine.

PCM comparison a.jpg

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4 hours ago, White93z34 said:

What car/year is your engine harness from?

98 Lumina LTZ

3 hours ago, 55trucker said:

I'm no expert when it comes to aftermarket tuning but your displayed schematics have a minor difference, the Lumina wiring harness is not quite the same when it comes to the signal for the oil pressure switch. If the PCM is not getting the signal then the PCM will shut down the engine.

In the Lumina, the oil pressure switch goes through the firewall to the gauge cluster, it's only there to show a warning light. I assumed the Impala was the same, though it went through the PCM first. But you're the second person to mention that specific difference in the diagrams. So, I pulled the F2 wire out of the C100 firewall connector, put a new pin in C2-19 and connected the two together. Started it up, it ran for a few seconds and shut off... Switched the VATS setting from 0 to 2 (default is 1), tried it again, same thing. I suppose I can go through another complete cycle of all three VATS settings, and then again with Injector Disable Time set to 0 instead of 4.

22 minutes ago, White93z34 said:

Is that actually the case on those PCMs? I don't think it is, but it could be. 

Any codes being logged?

There are codes, but all of them are EVAP related.

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I think as a whole you are fine with the VATS issue. My understanding is that it won't start at all with it being unhappy.

Maybe peruse the oil pressure issue, If It were me troubleshooting that I'd pull up the manual for a 04' Impala via ESI or whatever resource you have at your disposal. And find the flowcharts for your issue/ oil pressure sending unit. Find what the normal operation looks like.... I'd imagine if you grounded that sensor it would be either normal or abnormal operation since its just a switch.... which if it is I don't know.

Looking at it again, it looks like the 04' PCM expects way more 5v reference then whats its being provided. those run the MAP, and various other sensors. With that PCM in verify 5v reference at the various sensors, MAP, TPS, IAC 

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1 hour ago, White93z34 said:

Is that actually the case on those PCMs? I don't think it is, but it could be. 

Any codes being logged?

Oh yeah,

 

SOP, the PCM needs to see the small current signal back from that pressure switch to keep the injector drivers & coils alive. If there's no oil pressure the switch doesn't close, the PCM won't let the engine run.  

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1 hour ago, Quaraxkad said:

98 Lumina LTZ

In the Lumina, the oil pressure switch goes through the firewall to the gauge cluster, it's only there to show a warning light. I assumed the Impala was the same, though it went through the PCM first. But you're the second person to mention that specific difference in the diagrams. So, I pulled the F2 wire out of the C100 firewall connector, put a new pin in C2-19 and connected the two together.

 

Where in the 98 Lumina harness is the pin location to the PCM for that circuit?

your schematic doesn't display it

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5 hours ago, 55trucker said:

Where in the 98 Lumina harness is the pin location to the PCM for that circuit?

your schematic doesn't display it

In the Lumina it only goes to the firewall C100, into the cabin for the gauge cluster warning light.

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7 hours ago, White93z34 said:

I think as a whole you are fine with the VATS issue. My understanding is that it won't start at all with it being unhappy. 

I've read nothing but conflicting information on that. Some say the car won't even start, some say it will start and shut off after a second or two. That's why this whole time I've been thinking it was a VATS disable issue.

7 hours ago, White93z34 said:

Maybe peruse the oil pressure issue, If It were me troubleshooting that I'd pull up the manual for a 04' Impala via ESI or whatever resource you have at your disposal. And find the flowcharts for your issue/ oil pressure sending unit. Find what the normal operation looks like.... I'd imagine if you grounded that sensor it would be either normal or abnormal operation since its just a switch.... which if it is I don't know. 

I might be getting confused here... The 04 Impala diagrams shows ENGINE OIL PRESSURE INDICATOR SWITCH (ABOVE STARTER). It has a two-pin connector, pin A goes to PCM C2-19 OIL PRESS SW, and pin B is grounded. So that's either open or grounded, no voltage. This seems like the sensor for the gauge cluster warning light, and not an actual data sensor for the PCM. If there is an actual 0-5v oil pressure sensor for the PCM. I don't see it.

The sensor I was looking at however is not above the starter like the diagram says, it's above the passenger side CV axle. In my wiring harness, that's got a 2 pin connector, one pin is grounded and the second pin leads to the firewall C100-F2. For the Lumina, this sensor is shown under the Instrument Cluster wiring diagrams, and the PCM diagrams don't show any other oil pressure sensor.

Of course, these diagrams might just be wrong, even though I think Mitchell's data is supposed to be good for wiring. I really would rather look it up in a REAL 04 Impala service manual. I'm keeping an eye out for a set on eBay.

04 Impala SS

PCM_04ImpalaSS.png

98 Lumina LTZ

PCM_98LuminaLTZ.png

 

7 hours ago, White93z34 said:

Looking at it again, it looks like the 04' PCM expects way more 5v reference then whats its being provided. those run the MAP, and various other sensors. With that PCM in verify 5v reference at the various sensors, MAP, TPS, IAC  

There are indeed way more 5v reference outputs on the Impala PCM. The Lumina harness splices those all together into two or three output pins. But as far as I can tell all sensors are getting their 5v, just from different pins. But now that you've mentioned it, what are the chances that Impala PCM is turning *off* one of the 5v outputs my Lumina harness is using...?

6 hours ago, 55trucker said:

SOP, the PCM needs to see the small current signal back from that pressure switch to keep the injector drivers & coils alive. If there's no oil pressure the switch doesn't close, the PCM won't let the engine run.  

Seeing that the sensor in the Impala diagram is either open or grounded, I tried both options. No change.

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Can you not edit the '00 GTP pcm to have the transmission settings from the '04?  Also: Have you compared the the actual '00 to '04 diagrams to try to determine a difference? If that pinout chart was made by someone, I wouldn't trust it fully. I should have probably read the entire thread before asking that question considering you actually posted the diagrams above.

edit: Another wiring diagram source to compare Mitchell(they're usually pretty good, but you can find inaccurate information from time to time. Same goes for any resource. Even the factory manuals have errors - found one a while back on a '94 Regal that could have thrown me off had I not checked "just in case." It was listing a wire as having full time power when it was actually switched.)  Follow this link, agree to the license agreement, then switch the Wiring tab and select the cars you want. http://www.bbbind.com/free-tsb/  

Edited by mfewtrail

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