89 Chrysler Voyager, SMEC Gurus Please Help

Hello everybody,

some weeks ago I've posted problems I had with my 89 Voyager.
It reported code 54 (although the signals from the distributor
looked great at the oscilloscpe screen), it was hard to start
and tended to stall at red lights when warmed up to full
operating temperature. It also engaged the a/c compressor every
10 seconds (but just for a single second!), even when I pulled
the cable from the low pressure switch!
I finally gave up searching for cabling and / or contact
problems. I went to a second hand parts dealer and bought a
used SMEC from another 89 Voyager. The SMEC I bought did not
have a Chrysler sticker with a parts number on it, so I was
unable to verify that it was exactly the same SMEC as the one
in my car, but these computers are extremely difficult to find
in Germany, so I just decided to drop $100 and give it a try.

Back home I swapped the SMEC.

Now the car is running great! No more "code 54", no more a/c
trouble, no more hard start procedures, no more stalling! Last
weekend I drove the car for 500 miles, fuel economy is good.

There are just two issues left: with the "new" SMEC I have a
little bit higher voltage than with the old one. Can this be
adjusted at the dealer? What is the maximum allowed voltage when
the engine is idling?
Second: I'm getting code 23 now, which should tell me that the
charge temperature sensor is malfunctioning. Well, my engine
(a 3 litre Mitsubishi) does not have that sensor! Is it possible
to "tell" the SMEC (using the dealer's computer system) that there
is no such sensor, or should I just let it live with that error,
or should I try to add that sensor to the car to complete the
system? If so, how can I connect a wire to the 60-way SMEC connector,
I do not have a connector for that sensor in my wire harness?

Thanks for your help,

Markus

 

I remember this report, yes.

On the other hand, this means your likelihood of getting the correct one
when you *do* find one is higher!

Terrific. Problems solved.

It cannot. The voltage regulation is fully integrated with the SMEC and is
nonadjustable. If voltage regulation fails or becomes problematic (e.g.
overly temperature sensitive such that your fernlichtgluehlampen act like
blitzlampen if you switch them on immediately after starting the engine in
very cold weather), then you either get a replacement SMEC (factory fix)
or you cleverly install an external voltage regulator -- THESE can be had
in adjustable form.

It is temperature sensitive. Factory spec is as follows by ambient
temperature °C at battery:


-18 to 10°C : 14.95V
10 to 38°C : 14.45V
38 to 66°C : 13.85V
66 to 93°C : 13.75V

I cannot confirm or correct this with the literature available to me at
this time. That is what is listed in several of the online code lists, but
codes differ from year to year, and unless you have got this equation from
Chrysler's own 1989 FWD service manual, do not be sure it refers to the
air intake temperature sensor (or "Charge temperature sensor" as you call
it). P

No. SMECs cannot be reprogrammed by the dealer's computer system.

Probably the easiest route. It's running well, getting good fuel economy..

...zie gesundt!

DS

 

Weird you vehicle should take a SMEC and not a SBEC as that was the later
iteration of the engine controller on your particular year model. If your
vehicle indeed does have a SMEC (2 connectors) then you probably got a
earlier SMEC where they used to have the charge temperature sensor screwed
into the intake manifold and your vehicle is a later model where the
computer extrapolated the charge temperature from the battery temp sensor
(which was really just a thermistor inside the SMEC/SBEC). I wouldn't worry
about it too much as when one sensor isn't available the computer either
substitutes a default value or uses a correction factor on some other sensor
(perhaps engine temp-who knows, you would have to speak to the engineer who
programmed the thing). What is your voltage and at what ambient
temperature?

 

AHA! Now checking that with a voltmeter it turns out that right now
with the "new" SMEC I have the right voltages; so I must have had a
low voltage system with that original broken SMEC, because the dash
panel voltmeter showed about 0.5 volts less before the swap.
Also my "Fernlicht" is quite normal (Hey, where did you learn German?).

Hmm, the thing about code 23 is "what they say on the net" and what my
Haynes manual says. I don't have CC manuals available. I was just
wondering if anybody knows that it is normal that within the model year
of 1989 Chrysler made 3.0L engines with and without the intake air
sensor. Is it possible that this is a difference e.g. between California
and Federal engine versions?
I'm just asking because it was around 1989 when CC really started selling
the Voyagers in Germany. Nevertheless at that time half of all the vehicles
registered in Germany were self-imported, that means we have a beautiful
mixup of Canadian, Federal and California versions and usually the German
Chrysler mechanics do not even know that these cars were different!

The Haynes manual says that 3.0L and 1991 and earlier 3.3L engines have
that "charge temperature sensor". They even supply a drawing about where
the sensor is located (passenger side of the intake air plenum, right above
the vacuum hose connector). At that very spot my Voyager's intake plenum
does not even have a blocked hole or something like that. I also don't
have an unused connector in that area.

That code 23, BTW, does not light up the "Check Engine" lamp.

Best regards,

Markus

 

Most of what I need to know I learned from my friend Peter:
http://members.aol.com/phw1auto/

It will pay you many times over to send to North America for the genuine
Chrysler Corp. manuals -- or watch for them on www.ebay.com . The Haynes
book is dreck!

DS

 

Incorrect. It is perfectly normal that the original poster's '89 Voyager
uses a SMEC. The SBEC was first used in 1990-model vehicles.

DS

 

Yes, of course my vehicle takes a SMEC. But that they went from dedicated
sensor (at intake plenum) to extrapolation from another sensor, that's new
to me. If this is the case, they must have done it in 1989, because the
dealer who sold me the replacement SMEC gave me the VIN of the vehicle from
which my replacement SMEC was taken out. So I could verify that both cars
were 1989 models (if the info was correct, however).

I would not mind to buy a sensor and connector, drill a hole into the
intake plenum to screw it in, but how should I attach the wires to that
60-way connector? I'm afraid I would need special crimp-on contacts to
snap the wires into the connector body...

See Daniel Stern's post. Turns out that I'm having the correct voltages
now and that I've had a low voltage condition with the broken SMEC.

Best regards,
Markus

 

According to my CC service manual for the 89 Caravan, the code 23
applies to the throttle body temperature sensor which is used on the
four cylinder engine only.

Code 23 is not listed in the 3.0 engine code list.

 

Some more information

The SMEC in both of my 89 Dodge Grand Caravans with the 3.0L engine
are marked with the CC part number - 5235097. If the part label is
missing, the part number can be obtained from inside the SMEC by using
a scanner such as the OTC System 2000.

The eBay auction had a new SMEC of this part number up for auction
this summer. The starting bid was $90 but there were no bidders.