7.4L Vortec PCM

[wheels87k5]

Looking for the pin outs for the 1999 7.4L Vortec PCM

Searching internet and not having much luck. I can find 4.8, 5.3 and 6.0 but not for 7.4.

Are the pin outs the same for all of them or are they different in any way?

 

[ZooMad75]

Looking for the pin outs for the 1999 7.4L Vortec PCM

Searching internet and not having much luck. I can find 4.8, 5.3 and 6.0 but not for 7.4.

Are the pin outs the same for all of them or are they different in any way?

I should be able to pull them out of the service manual. Give me a little bit and I'll get them to you.

 

[TreeFarm]

They are different a bit but not a ton. I have one floating around somewhere from when I did a LS in place of a 7.4 in my 98. Let me look around. If i recall correctly I had to email a guy to have him send it to me.

Okay, These are the two things I used for my swap. I cant be sure they are 100% for your truck.

Lt1swap Vcm connector end views

 

[wheels87k5]

The reason I'm needing the pin out for this PCM is because I don't have the connector for the oil pressure sensor and I may need to add it myself. I've emailed the group that did the harness rewire and not getting a response. I'm trying to get all these little things done because time is flying by so fast. And BB20 is just around the corner.

Thanks for the help.

 

[ZooMad75]

Send me a PM with your email address. I've got the page with the connector end view for C1, C2, C3 and C4 connectors at the PCM.

 

[TreeFarm]

The reason I'm needing the pin out for this PCM is because I don't have the connector for the oil pressure sensor and I may need to add it myself. I've emailed the group that did the harness rewire and not getting a response. I'm trying to get all these little things done because time is flying by so fast. And BB20 is just around the corner.

Thanks for the help.

If I recall correctly, The oil pressure goes straight to the instrument cluster. not the pcm. It should be a 4 pin connector, sensor ground, sensor signal. then fuel pump in and fuel pump out. The sensor bypasses the fuel pump relay when there is oil pressure.

Note sensor ground is not chassis ground. This is black with white stripe. its a reference ground the pcm and gauges use.

on the factory 7.4 harness this would have gone through the C200 connector behind the glove box on the gmt400 I believe. So that may have been removed for your swap harness.

 

[wheels87k5]

If I recall correctly, The oil pressure goes straight to the instrument cluster. not the pcm. It should be a 4 pin connector, sensor ground, sensor signal. then fuel pump in and fuel pump out. The sensor bypasses the fuel pump relay when there is oil pressure.

Note sensor ground is not chassis ground. This is black with white stripe. its a reference ground the pcm and gauges use.

How would that hook up to aftermarket gauges? I'm using Autometer. I know the sensor connects at the back of the engine. And I have an oil pressure sending unit next to the oil filter. That's what I use for the oil gauge.

 

[TreeFarm]

How would that hook up to aftermarket gauges? I'm using Autometer. I know the sensor connects at the back of the engine. And I have an oil pressure sending unit next to the oil filter. That's what I use for the oil gauge.

If you don't have a connector for it in your engine harness, then they are not using it for back up fuel pump control so you don't need the oem one anymore.

Personally I would just replace the sensor with an auto meter one compatible with your gauge and run your own wire.

or you can find which one of the pins on the sensor is for the actual pressure reading, and connect that to the gauge. but that may not be using the same resistance scale as auto meter is. You can buy the connectors on rock auto .

 

[wheels87k5]

Thanks to both of you for the PCM pin outs. I didn't realize the 5.7 was the same as the 7.4. I had seen that page before but I didn't see a reference to it being for the 7.4.

When you get the chance, could you go to my build, page 16, and take a look at the connectors I have questions on. I may have figured out two of them but there are 3 more that I need to identify.