SaabCentral Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
2,611 Posts
Discussion Starter · #1 ·
Hello Everyone.

A quick search will reveal that the mysterious Motronic code 73 is relatively common yet impossible(?) to fix. Herein, I will describe my adventure with this code. The idea would be to prevent unnecessary repairs, as I have done.

The car:
1994 900S 2.3L Gasoline 5-Speed with Bosch Motronic 2.10.2 ECU
184000 miles

My CEL came on roughly two years ago and I read the code with the traditional blinking method. The code I got was 73 - Adaptation, Short Time according to the British Haynes service manual. This code was so ambiguous that I sent the car to my saab mechanic and had him use a TechII to get a real reading. According to him, the engine was running excessively lean during idle which implies either a dying sensor (O2, MAF) or an air leak.

I read around a bit and discovered that the original saab O2 uses a three wire system (2 heater, 1 signal) and uses the exhaust system connection as a ground reference. Cleaning the threads for the O2 can help, however, the resistance can come from elsewhere in the engine (namely, the connection with the cylinder head). I've now adapted my O2 to 4 wires with a direct ground connection to the vehicle chassis.
CEL: Not Fixed.

I replaced the O2 sensor entirely with a Bosch OEM.
CEL: Not Fixed.

I thoroughly checked the MAF with a precision anemometer. Everything was normal.
CEL: Not Fixed.

I replaced every vacuum hose and thoroughly inspected the air intake system including the IAC, TPS, resonator, etc.
CEL: Not Fixed.

Someone told me that the problem could be an intermittently faulty timing reference (cam/crank sensor). I replaced the crank sensor entirely (easy and cheap) and checked the cam sensor with an oscilloscope. Both seem to be working fine.
CEL: Not Fixed.

The final thing I discovered was this.
Check 101-1471. This states that the Motronic 2.10.2 can sometimes throw incorrect idle adaptation codes when no fault is present. I'm not sure I believe this since there's no explanation given, but at this point it might be what I accept as final (unless someone can correct me).
CEL: Unreliable?

So, my conclusion is that I've spent too much time and money tracking down this problem, and I don't want other people to do the same. If it turns out that the CEL is total BS, I'm going to be extremely angry with Bosch.

BTW, the Motronic CEL can be reset by removing fuse #28 for a few minutes. That saves you having to enter the radio code. However, the code is kept in non-volatile memory so it can still be read with a techII. It just turns out the light until the code gets thrown again.

Also, the CEL can be permanently disabled very easily by cutting the yellow/green wire (pin #22 I believe) from the ECU. This is not recommended though.

I hope this post is a help to those of you who are as frustrated as I am. Also, anyone who knows better than me, please don't hesitate to correct me.

Have a nice day!

Darren
 

·
Registered
Joined
·
21,583 Posts
Thanks, Darren, for all the good ,well presented info.

This is now another favorite...which may help someone in the future.
 

·
Registered
Joined
·
719 Posts
Darren, See below....
Darren900 said:
Hello Everyone.

A quick search will reveal that the mysterious Motronic code 73 is relatively common yet impossible(?) to fix. Herein, I will describe my adventure with this code. The idea would be to prevent unnecessary repairs, as I have done.

The car:
1994 900S 2.3L Gasoline 5-Speed with Bosch Motronic 2.10.2 ECU
184000 miles

My CEL came on roughly two years ago and I read the code with the traditional blinking method. The code I got was 73 - Adaptation, Short Time according to the British Haynes service manual. This code was so ambiguous that I sent the car to my saab mechanic and had him use a TechII to get a real reading. According to him, the engine was running excessively lean during idle which implies either a dying sensor (O2, MAF) or an air leak.

I read around a bit and discovered that the original saab O2 uses a three wire system (2 heater, 1 signal) and uses the exhaust system connection as a ground reference. Cleaning the threads for the O2 can help, however, the resistance can come from elsewhere in the engine (namely, the connection with the cylinder head). I've now adapted my O2 to 4 wires with a direct ground connection to the vehicle chassis.
CEL: Not Fixed.

I replaced the O2 sensor entirely with a Bosch OEM.
CEL: Not Fixed.

I thoroughly checked the MAF with a precision anemometer. Everything was normal.
CEL: Not Fixed. I had a "hot" bucking and intermitent stalling issue with my 94 900S 2.3L 5sp but no codes. After weeks of trouble shooting I took a bow and left the pro's have it. Two weeks of diagnostics showed nothing (that fixed it anyway)! Both the Tech and I had checked and rechecked everything. The Technician "swapped" parts. It turned out to be the MAF even though it tested good and no codes were being generated. So don't dismiss it....
BTW... I found that the 8 valve KIA Sportage used the same MAF as the 94 and 95 Saabs (Bosch 0280217 105). Becareful though and make sure the part number on the bottom matches yours. There are (2) kinds shared and they are different. The KIA 16V, if I remember correctly is the same as 97-98 Saabs (Bosch 0280217 116???). MUCH cheaper and there are aftermarket options if you look around and don't mind non OE.

I replaced every vacuum hose and thoroughly inspected the air intake system including the IAC, TPS, resonator, etc.
CEL: Not Fixed.

Someone told me that the problem could be an intermittently faulty timing reference (cam/crank sensor). I replaced the crank sensor entirely (easy and cheap) and checked the cam sensor with an oscilloscope. Both seem to be working fine.
CEL: Not Fixed.

The final thing I discovered was this.
Check 101-1471. This states that the Motronic 2.10.2 can sometimes throw incorrect idle adaptation codes when no fault is present. I'm not sure I believe this since there's no explanation given, but at this point it might be what I accept as final (unless someone can correct me).
CEL: Unreliable?

So, my conclusion is that I've spent too much time and money tracking down this problem, and I don't want other people to do the same. If it turns out that the CEL is total BS, I'm going to be extremely angry with Bosch.

BTW, the Motronic CEL can be reset by removing fuse #28 for a few minutes. That saves you having to enter the radio code. However, the code is kept in non-volatile memory so it can still be read with a techII. It just turns out the light until the code gets thrown again.

Also, the CEL can be permanently disabled very easily by cutting the yellow/green wire (pin #22 I believe) from the ECU. This is not recommended though.

I hope this post is a help to those of you who are as frustrated as I am. Also, anyone who knows better than me, please don't hesitate to correct me.

Have a nice day!

Darren
 

·
Registered
Joined
·
2,611 Posts
Discussion Starter · #4 ·
Voila! Attention everyone! I have finally resolved this issue. It turns out the ELCD purge valve had crapped out on me and the engine was sucking un-metered air through the charcoal canister. For some reason, it stuck in the open position whereas it should have closed on failure.

So in the end, it was a vacuum leak, but one that was so slow as to not cause any other indicative problems.

I now have 198200 miles on the car and no CEL.

Have a great day everyone!

Darren
 

·
Registered
Joined
·
21,583 Posts
This does point out the utter complexity that todays vehicles are straddled with.Its takes a team effort today....

Good that the ending was successful and that good persevered..:cheesy: .
 

·
Registered
Joined
·
352 Posts
I have the same code. Where is this ELCD purge valve? Easy to fix / replace?

Voila! Attention everyone! I have finally resolved this issue. It turns out the ELCD purge valve had crapped out on me and the engine was sucking un-metered air through the charcoal canister. For some reason, it stuck in the open position whereas it should have closed on failure.

So in the end, it was a vacuum leak, but one that was so slow as to not cause any other indicative problems.

I now have 198200 miles on the car and no CEL.

Have a great day everyone!

Darren
 

·
Registered
Joined
·
21,583 Posts
1 - 8 of 8 Posts
Top