Chrysler Repair/Limp mode-1992 Lebaron: MAP sensor
QUESTION: Lebaron with V6 and 4 speed transmission makes hard shift going 3rd to OD (I think that is the shift, loud double attempt up and down and may go to limp mode). However if I keep rpms between 1700-1800 it will shift through all with no problem. At 2100-2300
it will not. I changed fluid and filter. Looking at the speed sensor I found that the wire had been stripped previously for checking with a meter. Voltage readings are 12.04V and 6.38V at
disconnected plug. Removing the connector while engine is running will alter idle so I assume it functions at least partially. Was going to check MAP and TPS next but thought I needed your help.
ANSWER: Hi Dave,
When the trans goes into limp mode the TCM does two things: it cuts out the transmission relay's output which results in the 2nd gear only limp (to minimize damage to the trans), and it puts a fault code in the transmission control module. To get the fault code there is a blue 6-pin socket (2 x 3 array) under the dash at the left hand end, called the 'data link connector'. A shop that has a code reader along with the Chrysler plug to fit the socket can access the transmission fault code number, two-digits. That is a separate socket from the one in the engine compartment that reads the engine control module. If you can get that number I can look up the meaning of the code and what are the possible reasons/solution for it.
I would doubt it is the MAP of TPS, rather it specifically is transmission related.
Thanks for the rating and nomination.
---------- FOLLOW-UP ----------
QUESTION: Hi Roland,
Since I was pointed towards the MAP and TPS I finished checking them. I
found the TPS functione smoothly and as expected. The MAP had 4.99VDC
supplied with just the ignition on. However, checking the idle voltage
between map sensor signal and supply I found 3.99 and at 2000rpms there
was 4.06. What should these values be?
I have the voltage values based upon the pressure readings stated as inches of Mercury. They range from 4.6v all the way down to 0.34v as vacuum changes from .39 to 29 inches of Mercury. But I don't have voltages based upon rpm. So long as the reading vary up and down as you manipulate the throttle I would not suspect the MAP. It is possible that the overall calibration of the MAP could be wrong and that might well cause a no-start. That happened to me once. You want to measure the voltage between the dark green/red and black/light blue wires at the sensor as those are the signal and reference (ground) wires.