Can't access CIS diagnostic fault codes on my 1990 300 TE wagon

[Ascension]

Sorry to keep bugging you guys with my fight and this car but don't know where to get info on these issues from folks I can really trust other than here. Car runs very well now but the AC is dead and it will not activate the cold start solenoid and fast idle. I think the issues may be related and here is whats going on and why I think that.

Tried to use my blink in the 16 pin diagnostic port today. Only 3 ports are active on this car and was able to pull codes off port 6 and 7 showed clear. However port 3 (CFI) was a different story. Connect my blink to port 3, the light activates at a reduced brightness and when you hit the button the light gets brighter but it will not activate the diagnostic mode and blink a code.

For some reason there is constant voltage on port 3 that should not be there and I strongly suspect the electronic engine controls are all dead. I know several here have experiance with the M103 and KE Jetronic system and I now suspect I may have a bad MAS Control unit in this car. However before I go farther would like some insight from those here who know the M103 KE Jetronic system if I'm on the right track or if there is something else that would cause this issue I'm missing.

 

[jhodg5ck]

Have you checkec codes @ X11 [with on/off ratio], key on ignition off?

Is this a MAS relay car? Or does she have seperate FPR and Klima? I forget which years are the cross over.

 

[Ascension]

Whats X11 the round port by the EZL drivers side? If so have no info how to.

 

[gerryvz]

Whats X11 the round port by the EZL drivers side? If so have no info how to.

yes, that is the X/11 port. You need a multimeter with duty cycle capability to check the duty cycle live while the engine is running. There should be information on this either here or on the 126board.com, which deals with CIS cars.

 

[gsxr]

yes, that is the X/11 port. You need a multimeter with duty cycle capability to check the duty cycle live while the engine is running. There should be information on this either here or on the 126board.com, which deals with CIS cars.

Gerry nailed it - any questions related to CIS need to be posted on the 126board. You'll find far more people there who know CIS, compared to this forum which is heavily LH-SFI focused.

 

[gerryvz]

Have you checkec codes @ X11 [with on/off ratio], key on ignition off?

Is this a MAS relay car? Or does she have seperate FPR and Klima? I forget which years are the cross over.

His car is going to have a separate FPR and Klima relay. As an M103, it's going to be a CIS-E car that is several years before the cross-over.

 

[Ascension]

Have you checkec codes @ X11 [with on/off ratio], key on ignition off?

Is this a MAS relay car? Or does she have seperate FPR and Klima? I forget which years are the cross over.

Yes this one has the MAS and I strongly suspect it may be the culprit.
From FCP's site for this car but RM has the same part much cheaper.

Mercedes MAS Control Unit - Programa 0115457932

Mercedes MAS Control Unit - Programa 0115457932

www.fcpeuro.com

I will bet North Birmingham has a few of the MAS relays as they have tons and tons of used parts for these cars. That's were I grabbed the tandem Vickers PS pump for $100 that's now on the wagon.

 

[Ascension]

His car is going to have a separate FPR and Klima relay. As an M103, its going to be a CIS-E car that is several years before the cross-over.

This one does have the MAS Gerry and I'm looking hard at it as the possible culprit here.

 

[Ascension]

yes, that is the X/11 port. You need a multimeter with duty cycle capability to check the duty cycle live while the engine is running. There should be information on this either here or on the 126board.com, which deals with CIS cars.

Thanks Gerry.

 

[gsxr]

I think he's referring to the control module shown below, labeled "MAS".

I don't speak CIS and have no idea what this thing does.

And CIS definitely does not have a mass airflow sensor like later EFI models do...

 

[gerryvz]

I believe I have a MAS from an M103 that I would be happy to sell for $40 shipped.

 

[Ascension]

I think hes referring to the control module shown below, labeled MAS.

I dont speak CIS and have no idea what this thing does.

1990 was the first year for the MAS system and yes the wagon has it. Because of what it controls I suspect this may be my problem. Car won't go into the cold start so I don't have enrichment and the fast idle on a cold start. Also can't pull diagnostics and the AC is dead. I suspect it all may be related because of what the MAS controls.

This is from the FCP site on the MAS:
Controls: Fuel Pump, RPM Control, Idle, A/C Compressor, Oxygen Sensor, Heater Onboard Diagnostics


However I have little experience with this system and getting any real info to diagnose a problem is very difficult.

PS have a post on the 126 forum in the CIS section and have had absolutely no response so far. I guess you guys here seem to be it for any credible help on this car.

Thanks for the responses and sorry to be a PITA on it.

 

[Ascension]

I believe I have a MAS from an M103 that I would be happy to sell for $40 shipped.

Will send you a PM Gerry thanks.

 

[Ascension]

Well looks like my wagon had a bad ECM. Tried a known good MAS yesterday and it had no effect so picked up a ECM from my buddy Paul over at Birmingham Benz today to try. Car instantly fired cold as it should and feels completely different now. This is my first with the M103 and it surprised me how responsive it suddenly became with working engine management. No where near the power level of my E 420 but was suddenly much more respectable than it was to drive in traffic.