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Thread: 16188051 PCM $EE for 1995 Corvette LT1

  1. #1
    Carb and Points! wsalminen's Avatar
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    16188051 PCM $EE for 1995 Corvette LT1

    I apologize if I'm posting incorrectly but this looked like the best area to post that I could figure out.

    I have a 1995 Corvette with an LT1 and the 16181333 PCM. I would like to get a backup PCM and was wondering if the 16188051 PCM will work since they are readily available and cheap. It looks like a few inputs are different or missing (e.g., the oil temperature on the Vette does not appear to be present on the 16188051 PCM). I'm more interested in being able to run the engine with the 16188051 PCM vs having all gauges functioning. I have all the necessary stuff for programming either PCM since I have been tuning my Vette with the current 16181333 PCM.

    I have searched various post and forums and it isn't 100% clear to me if the 16188051 will work.

    Thanks!

  2. #2
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    it os compatible PCM, it is all about flash whether it will use some signals or not.

    best regards

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    Quote Originally Posted by wsalminen View Post
    I apologize if I'm posting incorrectly but this looked like the best area to post that I could figure out.

    I have a 1995 Corvette with an LT1 and the 16181333 PCM. I would like to get a backup PCM and was wondering if the 16188051 PCM will work since they are readily available and cheap. It looks like a few inputs are different or missing (e.g., the oil temperature on the Vette does not appear to be present on the 16188051 PCM). I'm more interested in being able to run the engine with the 16188051 PCM vs having all gauges functioning. I have all the necessary stuff for programming either PCM since I have been tuning my Vette with the current 16181333 PCM.

    I have searched various post and forums and it isn't 100% clear to me if the 16188051 will work.

    Thanks!
    Hiya,
    If you can get them cheap, I'd like a couple 8051's :) PM me if I can paypal you for a couple or even one.
    -Carl

  4. #4
    LT1 specialist steveo's Avatar
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    the 16181333 has a few extra chips that probably help with some prototype OBD-II emissions testing stuff that is not available in the 16188051.

    this extra stuff wont affect you in real life and in reality was never used by GM

    you do have to reflash the 8051 first or it wont work on the bus with the CCM (the 8051 by default is the bus master, but in the corvette the CCM is the bus master)

    reflashing the 8051 in the car might require you to pull the fuse for the CCM until that first reflash is done?

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    Carb and Points! wsalminen's Avatar
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    Thanks everyone for the great information!

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    Carb and Points! wsalminen's Avatar
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    It looks like my local yards have some but I haven't picked any up yet. One quoted me $125- not cheap but a lot cheaper than the rarer 16181333.

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    Carb and Points! wsalminen's Avatar
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    ECU1.jpgECU2.jpgECU3.jpg

    I ended up buying a 16188051 from a 1995 Impala SS. I got it from a yard in Kentucky for $90 w/ shipping. They also threw in the harness with a foot of wiring. I have the wiring diagram for my 1995 Vette and found the 1995 Impala SS wiring diagram online. The biggest concern I had was one or two sensor grounds on the Impala were purple instead of black- once I got the wiring diagram, it made me more confident of hooking everything up. I basically connected all the grounds togethers into one wire (black negative arrow in the pic) and all the power sources into a second wire (red positive arow in the pic). The serial line was just a single wire. I bought an OBD2 connector off Amazon and wired the 2 grounds to the bundle of negatives from the harness, the positive to the bundles of positives from the harness, and the serial data line to the serial data line of the harness. I connected the positive and negative wires to a 12V battery that I made sure was charged up and plugged in my ALDL cord to the OBD2 connector and the USB end to my computer as normal. I first made sure I could download the existing Impala bin. Once that worked, I flashed my latest Vette bin to the ECU and it worked!

    I then swapped the Vette 16181333 for the 16188051 Impala ECU and kept my fingers crossed. Everything worked great. What really surprised me is that the tach and oil temp gauges worked since the Impala didn't have those outputs. Pretty cool having a backup for cheap and everything is working. The one I'm not 100% sure about is the ASR spark retard since the Impala doesn't have that and it looks like other F-bodies have that signal on a different pin vs. the Vette. It doesn't really matter to me since I always turn the ASR off. The Vette seemed to drive normal and no weird ASR issues- the engine is a 383 and the ASR doesn't like to play nice with all that torque so I always turn it off.

    Thanks again for everyone's advice and hopefully some of this extra info is helpful to others.

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    When you say the oil temp gauge works, do you mean the analog or the digital? The analog on the C4 is a separate circuit that doesn't involve the PCM. The digital, on the other hand, does and goes from the PCM to the CCM to the instrument cluster I believe. And why were you surprised the tach worked? It's been a while since I looked at the wiring diagram, but I don't believe that signal comes from the PCM to the cluster, but comes off the negative side of the coil as is traditional on the C4. And does the digital coolant temp work too?

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    Both the oil temp I/P sweep gauge and digital (via the LCD panel- the one where you can switch between coolant temp, oil temp, and voltage) gauges work. For the oil temp on the 1995 (at least according to the factory service manual I have- GM version), the oil temp sensor feeds the PCM and also the I/P gauge. When I data log, I can also get the oil temp sensor reading from the PCM so I'm assuming at least one of the feeds is a digital output from the PCM. I looked at the CCM inputs/outputs and didn't see the oil temp going into or out of it but I only looked quickly.

    For the tach, with the optispark, I think the PCM takes the optispark signals and puts them as a tach output (pin A13 white wire) for various uses (e.g., I/P gauge, EBTCM). I tapped into that white wire for the tach signal for my shift light and it works great. I don't see a tach feed directly from the coil itself.

    Both the I/P coolant sweep gauge and digital gauge (via that LCD panel) work. Definitely interesting learning about all the inputs/outputs on an LT1.

  10. #10
    LT1 specialist steveo's Avatar
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    the tach signal does come from the optispark through the ECM

    pretty much every engine and transmission sensor feeds the ECM. cars that don't use those sensors (EGR position, oil temperature, rear o2 sensor, etc) still have the inputs and log the sensor data so we can use those for additional sensors sometimes

    except the tach, the ECM doesn't have separate outputs for most of its sensors, but instead relays the data to the CCM or BCM via the ALDL bus, that then controls the dashboards gauges.

    the f-body doesn't really utilize this, it has a seperate temp sensor for its temp gauge and gets just the tach from the ECM.

    the y-body you'll notice when you're datalogging that probably a few of your instruments like oil temp go dead, these are the ones that are ALDL gauges, because once the datalogger has taken over the bus, those other messages stop.

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