Speedometer with new Engine

issacc1 · Feb 13, 2024

Hey all, I have a 1992 GMC k1500. i recently changed the engine to a 350 with the Edelbrock ProFlo 4 EFI. After getting the truck running and everything wired up i noticed my Speedometer no longer works. I took the old ECU out since it was no longer needed and I'm assuming that is the reasoning.

I'm looking to see if anyone has the wiring diagram for the VSS to Instrument cluster. Also, if anyone know what i have to do to get the speedometer working again. Any help is appreciated.

Thanks in advance!

AK49BWL · Feb 13, 2024

Did you take out the little white box under the glove box too? That's the vehicle speed buffer module that converts the VSS signal for the cluster, ECM, and ABS. The ECM only receives the buffer module signal in the early trucks.

This is for a 94 but 92 is the same as far as the VSS system. https://www.ak49bwl.com/other/wires/1994K1500/Cluster.pdf

issacc1 · Feb 13, 2024

The VSSB is still in the truck. Although I have to clips that are not plugged in. I have attached pictures of them. As you can see a white wire was cut but that is for the tachometer for the ProFlo to instrument cluster.

Is there a wire I need to cut and splice to another wire For the speedometer to work?

AK49BWL said:
Did you take out the little white box under the glove box too? That's the vehicle speed buffer module that converts the VSS signal for the cluster, ECM, and ABS. The ECM only receives the buffer module signal in the early trucks.

This is for a 94 but 92 is the same as far as the VSS system. https://www.ak49bwl.com/other/wires/1994K1500/Cluster.pdf

Komet · Feb 13, 2024

Speedo should be LT BLU / BLK going into the DRAC. You can find all these diagrams in the factory service manuals available for download here with a search.

issacc1 · Feb 13, 2024

Komet said:
Speedo should be LT BLU / BLK going into the DRAC. You can find all these diagrams in the factory service manuals available for download here with a search.

Would you happen to know where it has to be connected?

Komet · Feb 13, 2024

issacc1 said:
Would you happen to know where it has to be connected?

That's the fun part for you to figure out. I hooked mine up to FiTech's speedometer out wire.

issacc1 · Feb 13, 2024

Komet said:
That's the fun part for you to figure out. I hooked mine up to FiTech's speedometer out wire.

Unfortunately the ProFlo 4 doesn’t have the speedometer out wire. But I assume it’s cause I’m running a 700r4.

AK49BWL · Feb 13, 2024

Check the Brake fuse, should be a 15A. Runs the RWAL ABS and the VSSB module. The module may also be powered/grounded through one of those disconnected connectors, so that's something else to consider.

Further looking through my diagrams indicate that the module is grounded at the front of the engine, so it's almost a sure bet that black/white wire in the second connector (third pic, next to the cut white wire) needs to be grounded and your speedometer will work again. I'd do a continuity check between the black/white wire at module pin 8 (next to the green/black wire) and ground, and if there's nothing there, try continuity between that black/white wire and the black/white in the disconnected connector you chopped the tach wire from. If there's continuity THERE, ground that wire.

issacc1 · Feb 14, 2024

AK49BWL said:
Check the Brake fuse, should be a 15A. Runs the RWAL ABS and the VSSB module. The module may also be powered/grounded through one of those disconnected connectors, so that's something else to consider.

Further looking through my diagrams indicate that the module is grounded at the front of the engine, so it's almost a sure bet that black/white wire in the second connector (third pic, next to the cut white wire) needs to be grounded and your speedometer will work again. I'd do a continuity check between the black/white wire at module pin 8 (next to the green/black wire) and ground, and if there's nothing there, try continuity between that black/white wire and the black/white in the disconnected connector you chopped the tach wire from. If there's continuity THERE, ground that wire.

Thank you sir for all your help! It’s now working properly. I appreciate your assistanc!

issacc1 · Feb 14, 2024

AK49BWL said:
Check the Brake fuse, should be a 15A. Runs the RWAL ABS and the VSSB module. The module may also be powered/grounded through one of those disconnected connectors, so that's something else to consider.

Further looking through my diagrams indicate that the module is grounded at the front of the engine, so it's almost a sure bet that black/white wire in the second connector (third pic, next to the cut white wire) needs to be grounded and your speedometer will work again. I'd do a continuity check between the black/white wire at module pin 8 (next to the green/black wire) and ground, and if there's nothing there, try continuity between that black/white wire and the black/white in the disconnected connector you chopped the tach wire from. If there's continuity THERE, ground that wire.

Hey AK49BWL, any Chance you would know that why now my parking break light stays on? All I did was cut the black/white wire from that in used clip and ground it it next to the firewall.

Thanks

Speedometer with new Engine

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AK49BWL

GMT400 Forever!

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Komet

I'm Awesome

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I'm Awesome

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GMT400 Forever!

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