88 Caravan 3.0 V6 persistent code 13

At my wit's end now. Code 13 keeps coming back on my 88 Dodge
Caravan 3.0 litre!

Dealer replaced the engine controller which kept the car trouble free
for a few months only. Then exactly the same problem came back. It
was damp but well above freezing here in Vancouver, British Columbia
when the trouble started again..

Symptoms: Engine starts and runs normally for 5 seconds, then dies
with Check Engine light on.

Then after warmup, it runs at a high idle, maybe 1800 rpm and
drives OK, unless starting on a hill, at which times it flat spots and
takes a floored pedal to go but it does go.

Codes are 12, 13, 55.

Code 13 means "MAP sensor no change from start to run".

Last week we poked around and replaced the MAP sensor with a new one.
That wasn't it. Pulled the 60-pin connector from the "computer"
(engine controller) and checked continuity from the MAP connector to
the 60-pin connector. Then we put it back together. At the time we
checked vaccum with a gauge - solid at 20 inches. Removed each vacuum
line to check as well. Had the battery terminal off to reset the
computer each time.

It worked for about a week but Code 13 came back.

Two weeks ago I looked at it again.

No gunk in the newly replaced MAP vacuum hose. No opens in the three
wires all the way to the 60-pin connector. Used a round file to
carefully burnish the contacts in the connector. Did not worry about
corrosion on the 3-month old engine controller.

To check the MAP voltage, I even soldered three test points right
into the cable harness near the engine controller to watch the MAP
voltage.

With ignition on and engine off, I can see the effect of blowing (1
volt change) and sucking (three volt change) into the vacuum port of
the MAP sensor so it seems to work.

With ignition on and engine on, I can see the swing in the MAP voltage
from +5 to +1.5 volts from engine off to engine on. BUT even with the
voltage swing, the same problem comes up: engine dies after 5 seconds
and CHECK ENGINE light comes on with a Code 13 read-out.

I had the big connector on and off about ten times that day.

Could the code 13 be bogus and triggered by another condition? Anyone
seen this kind of persistence of Code 13 before?

I may have to give up so would be grateful for suggestions.

 

Normally I'd say corrosion somewhere. Check your grounds, very important!

But in this case I'd go to a wrecking yard and get another engine controller
just to be sure.

Ted

 

The engine controller *is* new. Only about 5 tanks of gas since
dealer replacement.

Set of symptoms that prompted replacement is identical to current
symptoms.

Good idea about checking the grounds. I am suspecting that giant
60-pin connector. The female terminals in that connector at the end
of the wiring harness are round stamped metal and may be losing
contact with the male pins on the controller module.

I wonder if those individual pins come out to be tightened up ...

 

There's no way your going to get anywhere without knowing what the computer
'sees'. You need a scan tool that reads the serial data. Find the factory
service manual and find the pins on the 60 way junction where it connects to
the computer, carefully examine these pins for spread or poor contact. You
want to be taking your voltage measurements as close to the 60 way as
possible so as to account for any problems mid wire.

 

The test wires I solder-spliced in were only one or two inches away
from the 60 way junction so the next logical step would be to check
the female pins on the connector itself. I only hope that they can
pull out, be crimped with pliers and then be put back in.

Serial data somewhere on the mostly parallel 60-pin connector? Didn't
know that. Why is there serial data and where would it be going?

 

They can, but you'll need the proper tools otherwise you risk
mangling the connectors and terminal block.

No, serial data transmitted by the PCM to the diagnostic
connector located under the hood.

For diagnostic purposes, it goes to the diagnostic connector
located on the left side of the engine compartment, slightly
behind the battery, near the row of relays mounted to the inner
fender. the data is meant to be retrieved by (initially) a
Chrysler DRB type scan tool although there numerous other
aftermarket scan tools available.

 

Has technical Service bulletin # 18-14-88 been performed?

How about TSB # 18-09-91?

These bulletins involve relocating the MAP sensor and installing
a bleed hose assembly to the MAP vacuum harness and a purge
jumper vacuum harness.

There should be/would have been a modification label attached
somewhere underhood if the TSB was done at some previous point.

 

I made a Molex pin remover for PC power connectors once from brass
tubing. However, I think I can use a sharp tool to bend the connector
a bit in the housing to ensure contact.

It's an 88. I will buy a reader when I get a newer vehicle and I need
to buy one. The vehicle might be too old for the newer code readers.

 

I don't hink either one has been performed. There wasn't anything
plugging the hose or sensor at all.

It's a 1988 model and the MAP sensor is on the alternator bracket.

 

Be very careful, as these vehicles age, the connectors and
terminal blocks get brittle.
Terminal extraction tools can be gotten from any of the major
tool suppliers or via the "Help" brand (Dorman) parts and
accessories line that many national parts chains carry.

If you mean waiting and getting a scan tool to fit a 96 or newer
vehicle, then yes, it most likely will *not* be capable of
communicating with your 1988 MY vehicle.
Check e-bay, there is lots of stuff for sale at pennies on the
dollar compared to what it sold for new.

 

You'd be best served to visit a Chrysler or Dodge dealership and
ask them to dig up the part numbers for or a copy of the latest
TSB (18-09-91) and then see if the parts are still available, if
so, install them before you dig any deeper. Once these TSBs were
issued/ implimented, cronic /false code 13 problems pretty much
evaporated.
If the parts are no longer available new, a visit to a wrecking
yard should yield everything you need. You're looking for a
plastic fitting "Tee'd" into the MAP sensor hose, at the end of
the "Tee" there is another plastic fitting (the bleed valve), the
distance it is installed from the MAP sensor is critical so pay
attention to how it's installed in the vacuum line.

 

I fixed my code 13 problem! Thanks to all and especially to Neil
Nelson for inspiring me to test all the possibilities. We were ready
to buy a near-new van but have to be in money-saving mode for awhile
yet. You would not believe how relieved I am this problem is fixed
and much money saved.

History:
After having the engine controller replaced, MAP sensor replaced,
checking for vacuum leaks and checking ALL the relevant electrical
connections ALL the way back to the module over literally months and
months, it still complained of a non-responsive MAP sensor.

Today I unplugged the 1/8" ID hose that the dealer had installed and
blew into it. It was clear, but there was a hint of an obstruction.
It was OIL!

Cleaning it out with solvent fixed the problem like magic!

Then I went by a wrecking yard to see if could could find the TSB
parts mentioned but there weren't any to be seen.

However, I did manage to see what the proper hose was and grabbed one.
It was 1/2" ID at the manifold end and 1/4" at the MAP sensor end. I
would have been problem-free longer had I the right tapered hose to
start with but the dealer who replaced the controller just assumed a
thin hose was all that was needed.

So blow-by must have been depositing oil into the intake and it built
up over weeks in the 1/8" (wrong) hose. I suspect this as after a
highway run, a huge cloud comes out when restarted the next day.
Never in town though.

I suppose that the by-now-discontinued TSB part must have been some
sort of oil trap to prevent gumming up the MAP sensor. That engine
controller must check for a change in MAP voltage too early, before
engine vacuum has had time to build up and get past the plug of oil,
no matter how runny it was in there.

- gw

 

Glad to see that you got it fixed.
Any time I replace a MAP sensor on a Chrysler product, I replace
the entire hose/tube with a length of 1/4" vacuum hose.

Shame on the dealership that originally replaced the SMEC without
doing a TSB search and/or just plain not recognising that this
thing should have the bleed valve installed.

FWIW, a friend went thru similar in the last week or two, 1989
Sundance w/ 4 cylinder, failed emissions test and recurring
cronic code 13. He did call a local Chrysler dealership parts
dept and was able to obtain the bleed valve. Although they may
be out of production, there should still be parts lingering on
the shelves at some dealerships.

 

Thanks for the info.

My 88 New Yorker is starting to throw intermittent 13's at me. I will check
the hose to the MAP sensor first !

Steve