W.E.G.

Repairing Harness/ECU computer connector.

If any of you have had the pleasure of disconnecting the wiring harness from your ECU computer, you know the connectors often show signs of degradation. For those of you who are unfamiliar, the ECU is mounted inside the cabin, on the passenger side, behind the dashboard. So, the ECU rides just above the passengers feet.

The perishable connectors that are the subject of this topic are comprised of two main parts:In my opinion, the degraded connectors between the wiring harness and the ECM are an often overlooked suspect when diagnosing intermittent drivability issues on these old cars. Think of it this way: If you had a device plugged into a wall outlet in a perpetually damp shed, an enclosure that is exposed to extreme seasonal variation in temperature, would you be surprised if the gadget malfunctioned due to degradation of the plug and/or the wall outlet?

Much credit to GM for designing an ECU and wiring-harness connector that does as well as ours do. In my opinion, the connectors do quite well – all things considered. But, they do eventually degrade. At what point does the connection FAIL, that’s harder to say. You might solve a mysterious intermittent drivability issue by simply unplugging the connectors from the ECU and re-plugging them. Theory being, this mechanical action will scrub corrosion on the union of the connectors and ECU, and the circuit that was intermittently open will stay closed after the un-plug/re-plug procedure.

I have been chasing all manner of drivability issues on my 1988 V6 Sport Coupe. (Yeah, I know… get rid of the V6 and “drop an LS in it.” Thank you very much. I already have one. This car will stay “mostly” original for the time being because I like it that way.

I’ve been playing around with the notion of modifying the EPROM chip, and also modifying the circuit board in my ECM. This has caused me to need to take the ECM out of the car, and reinstall it several times recently. The big black blocky plugs seem to be holding up. But, the “clips” that secure the plug to the ECM socket are brittle and doing badly – to the point that the clips are broken or outright missing.

Fortunately (and somewhat to my amazement), you can actually buy NEW clips for these harness/ECM plugs. Hawks sells them. This is the link to the two-plug set that fits my car, and most third gen cars.
http://www.hawksmotorsports.com/ecm-...tpi-88-92-tbi/
There is a second set that fits three-plug ECU’s.
http://www.hawksmotorsports.com/ecm-...ors-90-92-tpi/

Here is a pic of what you get if you order the $16 part from Hawks:



It seems that its mainly the clips that fail, since you have to flex the clips to disengage wiring harness from the plug-socket in the ECU. You have to buy the clips and plugs if you order. The clips are not available separately.

Here is a pic of the failed clip on the small plug on my car. Missing from the connector is the push-tab (allows you to “un-clip” the plug from the ECU) and also one of the hooks engages with the plug to keep the clip and the plug together as a single unit. These bits have missing for as long as I’ve had the car.



On that same connector, if you turn it 180 degrees to view the opposite side, you can see the clip is outright missing.

W.E.G.

The new blue comb-and-hook “clips” install easily. Remove any broken bits, and the new part clips right in. Pay attention to the orientation of the thumb-release. Install the blue clip with the thumb release on the same side for convenience and consistency. I’m not sure if it really matters from a functionality perspective if you keep them on the same side. But, I kept mine on the same side deliberately.


Ready to be installed:



Installed:

W.E.G.

Here, we have both plugs ready to re-install to the ECU. One has new blue clips. The other still has the old clips.




Here is the same pair of plugs, but showing the opposite sides. Note that the big plug has a grey-colored comb-clip.

W.E.G.

Here we have both connectors attached to the ECU. Note that the thumb-tabs for each connector are oriented on the same respective side of the big blocky plug. When the ECU is secured behind the dash the thumb-tabs are oriented so that you can reach the thumb-tab is on the firewall side of the ECU. This is the natural position that your thumb will contact if you reach under the dash, and need to un-plug the connectors from the ECU.

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And, lastly we have the ECU going for a test-ride. I just lay it on top of a moving blanket during test-rides. Saves having to fish it up under the dash for no good reason if I’m going to be removing it for my ongoing science project as soon as the test-ride is over.

Two things to note in the pic. One significant, the other not so much. The white plastic thing is a cradle that holds the ECU when it is installed behind the dash. The cradle is important. Because of clearances, I haven’t figured out how to get the ECU out of the cradle without removing (two screws) the cradle from dash assembly. The other dangling three wires is a courtesy light that is operated by a plunger-switch in the door jamb. That wire is my nemesis when I’m doing anything with the ECU. I managed to break one of the wires going to the plunger this time around. No love lost there.

Drew

iTrader: (58)

Mouser carries many of the GM/Packard Electric Division/Delphi connectors, pins, terminal position assurance keepers, weather seals, etc. The hardest part is finding the part numbers in the Delphi catalog or searching Mouser's website for the correct connector. They're generally very affordable too.