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Thread: Is there an Oil Pressure and Water Temp. output signal on 95 LT1 PCM ?

  1. #1
    Electronic Ignition!
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    Is there an Oil Pressure and Water Temp. output signal on 95 LT1 PCM ?

    Hey Guys
    I looked through the 95 LT1 wiring diagrams but did not see a pinout labeled oil pressure.
    I have a Tech Rods stand-alone wiring harness for 1995 LT1 & 4l60E that I would like to get connected to the wiring of a 93 s10 Blazer instrument cluster. I was using mechanical gauges for water temperture and oil pressure but want to have the dash gauge work.
    Thanks for any help Ken

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    those should both be discrete sensors and the guages for them should be driven directly from the sensors themselves.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  3. #3
    Fuel Injected!
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    The gauges use their own sensors that are completely separate from the fuel injection system. An LT1 typically had the coolant temperature sensor in the side of the passenger head and the oil pressure sensor in the port at the back of the block just behind the intake manifold. The EFI system uses the coolant temperature probe that is installed in the water pump.

  4. #4
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    I know the oil pressure sensor is connected to the engine pcm wiring harness but there is no output wires for the oil pressure gauge on the harness.
    I will try talking to Tech Rods tomorrow at lunch and see what they say about tapping into the wires to feed the gauge cluster. I have already printed the wiring diagrams for the s10 so I can tie them into

    As for the Coolant Sensor I try to find the right connector for the sensor and put into the passenger side cylinder head like lionelhutz mentioned.
    This where I had my mechanical temp gauge located.

    Thanks for the replys

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    i'm looking at the diagram of a 95 camaro LT1 and i'm not seeing an oil pressure input to the PCM, just one for the guage. i'm not seeing it in the corvette application either.... oil temperature shows up for that one though.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  6. #6
    Fuel Injected!
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    I agree, oil pressure was definitely not an input to the PCM. Is this connection down by the oil filter? That's where the Vette had the oil temperature probe installed.

  7. #7
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    I did not see the oil pressure sensor either on the pcm diagrams just thought I had missed it. Would it have some thing to do with Oil Life /Oil Change light. I think these cars had that feature. Maybe it the temperture that I'm thinking about.

    The connection is on the oil pressure sensor at the back of the block on the driver's side.
    Down near the oil filter is where I had the mechanical gauge connected. Hopefully Tech Rods can fill me in.

    Here is the link to Techrods 94-95 LT1 wiring harness if your interested.
    http://techrods.com/Products/Engine%...4-95%20LT1.htm
    Last edited by nchittman; 12-18-2013 at 08:00 AM. Reason: Added link

  8. #8
    Fuel Injected!
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    Taking a quick look, it appears to be a oil pressure switch (not sensor, switch) connector. On the early GM fuel injection stuff they put an oil pressure switch across the fuel pump relay. There has been many a thread about this switch being used to control the fuel pump once the engine is running but I have never seen any evidence of that being true. From my experience, it is simply a backup to the fuel pump relay only and I've eliminated it without any issues. I didn't believe it was ever used on a LT1 but it may have been on the early years.

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    Quote Originally Posted by lionelhutz View Post
    There has been many a thread about this switch being used to control the fuel pump once the engine is running but I have never seen any evidence of that being true. From my experience, it is simply a backup to the fuel pump relay only and I've eliminated it without any issues.
    both, really, in every application i've inspected the schematics for. i'm sure there will be exceptions though.

    once the engine is running and oil pressure rises above the ~4PSI threshold, the current used to drive the fuel pump is shared between the relay and the oil pressure switch. if one of them fails, the other takes all of the load and the engine continues to run.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  10. #10
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    Alright so I will need to install an oil pressure sensor and wiring to connect it to the Blazer's harness. I have not heard back from Techrods yet, had to email could not find a phone #to call at lunch. Time for some internet hunting. Thanks for the replys guys it helped me alot.

  11. #11
    Fuel Injected!
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    I looked through the '96 schematics. I have the GM electronic version '96 to '05 so that's what I looked at. The LT1 was used in the B-body cars, the F-body cars and the Y-body cars. There is no oil pressure switch shown for the B-body and F-body applications but there is an oil pressure switch shown for the Y-body application. I also have other versions of 94-96 F-body schematics and the oil pressure switch is not shown in any of them. Finally, I have been through both an earlier model F-body and B-body harness wire by wire and I can tell you 100% the switch was not in those harnesses.

    So, you can decide if you want to use that switch to back-up the fuel pressure relay or not. You can just tie it off in the harness if you want to and it will still work just fine unless the fuel pump relay fails and then you lose fuel.

    Knowing this it's easy to see what they did. The harness plug is for a 3-terminal sensor with 2 terminals in use. Looking up a '96 Corvette oil pressure sensor finds this thing.

    http://www.ebay.com/itm/ACDelco-1020...item43c2bc0c35

    So, the 2 wires they use are the oil pressure switch and the 3rd terminal is the oil gauge sender. If they would provide the 3rd wire in the pigtail you could use one of those sensors I linked for the both functions and keep all the connectors plugged in and looking neat.

  12. #12
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    So the LT1 Camaro's, Caprice and Impala's did not have factory oil pressure gauges but my little V6 S10blazer had one. That's Odd.

    Lionel thanks alot for the time you spent on this, Hopefully I can help you out some way. Let me know how?? Maybe Structural Welding Info?

    I'm going to see if Techrods can supply me with the the correct oil pressure switch / sender connector and the coolant sensor connector with wiring. This will be great to have all my gauges working. Thanks Again

    Well I decide to go take a quick look at what oil pressure switch I have and it the 3 terminal. But the connector doesn't have the third wire. I maybe able to go down to our local auto electrical specialist and either have him add the wire to my three terminal connector or sell me the terminal. Thanks Again might get it done this weekend.
    Last edited by nchittman; 12-19-2013 at 06:01 PM. Reason: Added Info

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    Quote Originally Posted by nchittman View Post
    So the LT1 Camaro's, Caprice and Impala's did not have factory oil pressure gauges but my little V6 S10blazer had one. That's Odd.
    they had them, but they were in no way connected to the PCM as described.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  14. #14
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    Just looked at some 95 & 97 Z28 camaro insturment cluster on ebay and both definnetly have Oil Pressure gauges. So the output from the sensor only goes to gauge cluster. The link to the AC Delco Oil Pressure sender/switch also fits 94 thru 97 Camaro's , Firebirds and Vetts.

    I agree that they have nothing to do with the PCM.
    Last edited by nchittman; 12-19-2013 at 06:32 PM.

  15. #15
    Fuel Injected!
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    Quote Originally Posted by nchittman View Post
    So the LT1 Camaro's, Caprice and Impala's did not have factory oil pressure gauges but my little V6 S10blazer had one. That's Odd.
    I think you confused oil pressure switch and oil pressure sensor in my previous post. The F-body LT1's did not have an oil pressure switch. They did have an oil pressure sensor. It looks like that switch/sensor combo you have but it only has the middle pin where you are missing the wire. There is no switch in it.

    FYI, you can also get one that has the outside 2 terminals and is only the switch. You got lucky you used the 3 terminal one that you need to get the gauge working. Good luck finding the terminal and wire.

    You could use the 3-terminal unit to replace either of the other 2 units. You can not use one of the other units to replace any of the other ones though.
    Last edited by lionelhutz; 12-19-2013 at 09:13 PM.

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