Chrysler Repair: error codes 0172, 1391, sensor operation, consecutive trips

Question
I have an 02 Pt Cruiser thats given the error codes p0172(Air/fuel mix is far too rich)(too much air is being added as a correction).

p1391(sometimes I cant see the cam or crank sensor singnal). What do they mean and how do I fix the problem?
This car has a 2.4L engine and automatic transmission.


Answer
Hi Hosie,
Unfortunately these two are not very specific, but take a look at those possibilities that seem to be easy, then tackle the more difficult ones until you find the cause:
P0172-FUEL SYSTEM 1/1 RICH
When Monitored: With the engine running in closed loop mode, the ambient/battery
temperature above (-7°C)20°F and altitude below 8500 ft.
Set Condition: If the PCM multiplies short term compensation by long term adaptive as
well as a purge fuel multiplier and the result is below a certain value for 30 seconds over
two trips, a freeze frame is stored, the MIL illuminates and a trouble code is stored.
Possible causes:
GOOD TRIP EQUAL TO ZERO
O2 SENSOR HEATER OPERATION
O2 SENSOR
EVAP PURGE SOLENOID OPERATION
O2 SIGNAL CIRCUIT
O2 RETURN CIRCUIT
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR
PCM

P1391
It says that one signal or the other (there are two signals) that come from an electronic sensor is disappearing momentarily at least 20 times in trip, during two consecutive trips. It suggests that either the sensor or its wiring or the engine part that the sensor observes is in some way faultly. It suggests that the wires to the sensor, or the part, or the sensor itself could be faulty and might be identified by visual inspection or testing with an electronic test device. The sensors are needed to time the sparking of the spark plugs and the injection of fuel.
In and of itself it is not of great concern until the signal it totally lost, in which case the engine will not run. So to me it would mean to be aware that this is happening and if the engine becomes notably losing its power or momentarily jerking that you need to find out which signal is missing and why because it may soon stop running.
I suspect one of the two sensors is beginning to fail. When it does so a code for which sensor will then be set and so the sensor would be replaced at that time. For now, if you have some experience in finding the sensors or you have a friend who does then simply checking that the wires are not damaged would be reasonable. Let me know which engine size size you have and I can describe where to find the sensors.

The list of procedures for evaluating the codes cover 8 pages in the manual which I can xerox and postal mail to you. If you would agree to send me back 3 42-cent stamps to cover my costs that would be most appreciated. Send me you postal mailing address if you would like me to do that, via a private option follow-up question.


Roland