911 SC oxs control module compatibility?

[Mike the mechanic]

Hey guys! Helping a friend... his 1983 SC had water infiltration, and the oxs unit under the passenger's seat is now toast.

His unit part number is 0280 800 006 and has one row of pins in its 35 pin connector.

We found a replacement unit which is apparently out of an 83 Sc as well, but the part number is different, 0280 800 055, and has two rows of pins in it's connector.

Part numbers of both units come up as both good for 83 models... anyone know for sure if the 055 is compatible with the 006 unit?

Thanks in advance!!

[AndrewCologne]

Very strange as a 0 280 800 006 unit normaly was built for being installed in 1980 SCs.
The 0 280 800 055 (yellow sticker) ist the correct device for '82-'83 SCs.

IF in your friends 1983 SC a 006 unit was installed, then the Lambda control shurely was messed up, as all connections for the cold enrichment (from 1981) ended up in a nirvana, means not connected as the specific pins are not existing/supported by the 1980s ECU socket (as only one row of pins).

EDIT: ECU Lamda control unit

Be shure you get a device from a dealer where the proper functioning is proofed and guaranteed or at least where you can give it back if not working properly. It should provide the correct 50% cruise and 65% accelerating dutycles when the sensor is not connected (where a 2 sec 75% duty cycle will be given on touching the gas when engine is cold).
With O2 sensor connected and with engine warm it moves over to closed loop state where the lambda controls the mixture via a verying duty cycle depending on the actual O2 sensor reading to force the engine's AFR to keep at stoich 14:1. ... You can (let it) check by using a dwell meter or a DMM with duty cycle mode.

[boyt911sc]

Andrew is spot on regarding the ECU.

‘80 (black label) 0-280-800-006
‘81 (blue label) 0-280-800-037
‘82 & ‘83 (yellow label) 0-280-800-055

Tony

[Mike the mechanic]

Thanks so much for the info guys! So, either this car had a wrong ecu in there the whole time, or it has a 1980 harness as well!

The harness connector has only one row of pins, which include an o2 sensor. Does the 1980 model have an o2 sensor? Does the 82-83 harness also have only one row of pins? I don't have an SC Bentley... and the diagrams I see online don't specify 82-83, but 1978 to 83, so it's a but confusing.

If I can track down what harness the car has, then I'll know what ecu I need to use.

Any tips regarding that?

[AndrewCologne]

Originally Posted by Mike the mechanic

The harness connector has only one row of pins, which include an o2 sensor. Does the 1980 model have an o2 sensor? Does the 82-83 harness also have only one row of pins?

You got me, Im sorry, ... the later ECUs did also come with one row of connected pins.
but with an additional terminal/Pin N° 14.

Also, check if there still exists the acceleration enrichment relay in that 1983 car.
As this is the one where its all about in the changes from 1980 to the later SCs and must be connected and proper working as well. Means you need both devices/modules for the lambda system of that 1983 car.





Its on the left side.

Does the 1980 model have an o2 sensor?

Yes it was the year where Porsche released the 911 SC coming with the bosch lambda based 3-way catalyst exhaust system.

[Mike the mechanic]

Andrew, yes, the car does have the enrichment relay in place.

Do you know anywhere online I can find both the 1980 and 82-83 wiring diagram so i can compare to see which one this car has?

Thanks again for your time!

[boyt911sc]

Mike,

What is the Bosch ID number on the WUR? Is it a -072 or -090. Keep us posted. Thanks.

Tony

[AndrewCologne]

Index of /Porsche/911/Wiring

Especially this one is what you need:
http://v12.dyndns.org/Porsche/911/Wiring/1982-porsche-911sc-wiring-diagram-part-five.jpg



And for comparison 80-83 see the attachment below.
http://andrewcologne.bplaced.net/911/Lambda_wiring_1980-1982.jpg

There you can see clearly which connections where used in 1980 and from 1981.

[High Life]

Originally Posted by AndrewCologne

Index of /Porsche/911/Wiring

Especially this one is what you need:
http://v12.dyndns.org/Porsche/911/Wiring/1982-porsche-911sc-wiring-diagram-part-five.jpg



And for comparison 80-83 see the attachment below.
http://andrewcologne.bplaced.net/911/Lambda_wiring_1980-1982.jpg

There you can see clearly which connections where used in 1980 and from 1981.

OOOH...

Thanks for this...

[Mike the mechanic]

Guys, thank you so much for the help with this. The harness is the correct one, and we now have the proper control unit for the year, but the car is still running poorly...albeit a bit better. There are more issues to track down but for now at least we have that part of it sorted! Thanks again!

[boyt911sc]

Originally Posted by Mike the mechanic

Guys, thank you so much for the help with this. The harness is the correct one, and we now have the proper control unit for the year, but the car is still running poorly...albeit a bit better. There are more issues to track down but for now at least we have that part of it sorted! Thanks again!

Mike,

The main difference between the enrichment harnesses for ‘80 and ‘81~’83:

‘80 SC uses the 6-pin plug connector for the ECU all six (6) being used.
Later SC’s use the 12-pin plug connector for the ECU with only 7 pins used.

Tony