I get code 51 on 1996 dodge caravan....fuel system lean---a lean air/fuel mixture has been indicated by an abnormally rich correction factor. The van runs fine when engine is cold but will sputter and won't accelerate sometimes when it is driven for a while. I drove it about 30miles this weekend and it ran fine. After about 30min of being turned off I started driving again and it started sputtering and died and I couldn't get it started again. The next morning it started right up and was running good. I'm afraid to drive it now for the fear of being stranded on the side of the road. It has been doing this for the past year but is now getting worse. I recently changed the fuel filter with no change....Now I,m wondering about the fuel pump. Any suggestions on what the problem could be.

I'm not sure what you mean by testing spark plugs. The diagnostic code defined as "system too rich, bank 2" indicates that the reading reported by the bank 2 cylinder bank (containing cylinders 2, 4, 6, and 8) is consistently reporting a rich exhaust mixture rather than a reading toggling between lean and rich. This might mean you have a fuel injector that is not providing the correct amount of fuel, a spark plug that is not properly burning the air/fuel mixture, an oxygen sensor issue, a wiring issue to the sensor, etc.

-Rod

That is a fuel mixture code indicating it is too rich. You definitely have some fuel control problems with this car.

P0171 Chrysler - Fuel System Lean

Possible causes
- Intake air leaks
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow (MAF) sensor
- Incorrect Positive Crankcase Ventilation (PCV) hose connection

Tech notes
If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replaced the air filter and clean the air flow meter. If the problem persist the front oxygen (O2) sensor may need to be replaced.

When is the code detected?
- Fuel injection system does not operate properly.
- The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)

Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Excessive Fuel Consumption


P0171 Chrysler Description
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the Malfunction Indicator Light (MIL) (2 trip detection logic).




P0171 Chrysler Fuel System 1 1 Lean

This is the closest I've come to the code you are looking for. I searched all Dodge codes and didn't see any with a "point 2" but I found code P0172. According to EngineCodes.com your fuel mixture is probably too rich. This is what the site had to say:

Possible Causes for this Code:
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Faulty Mass Air Flow (MAF) sensor
Read more: http://engine-codes.com/p0172_dodge.html#ixzz35waCcFhN

This code is detected when:
- Fuel injection system does not operate properly.
- The amount of mixture ratio compensation is too large. (The mixture ratio is too rich.)
Read more: http://engine-codes.com/p0172_dodge.html#ixzz35waXE700

Possible symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)
- Excessive Fuel Consumption
Read more: http://engine-codes.com/p0172_dodge.html#ixzz35waruoIU


P0172 Dodge Code Description:

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic).
Read more: http://engine-codes.com/p0172_dodge.html#ixzz35wbfFdyj


Hope this helps!

Well, code 51 means the O2 sensor is telling the computer the fuel mixture is lean. So the computer tries to make the mixture rich by opening the injectors longer. I doubt the sensor has failed, but rather your fuel pressure is low.
If the sensor has failed and pressure is normal, you should have black smoke coming out the exhaust pipe.

Combustion engines operate by burning an air/fuel mixture of about 14.7 to 1-14.7 parts air to 1 part fuel. When the air ratio goes below 14.7 parts, this is called a "rich" mixture. If the air rises above 14.7 parts, it is called a "lean" mixture.

Rich Mixture = Too much fuel, not enough air
Lean Mixture = Too much air, not enough fuel

To keep the engine running properly, the Engine Control Module measures the oxygen content in the exhaust with oxygen sensors and makes adjustments to the mixture by injecting more or less fuel.

P0507 Idle Control System RPM Higher Than Expected
P2187 System too lean at idle

Things to check:
1. MAF
2. Fuel pressure, fuel pump flow rate

Do you have cold air intake?

Run a fuel system cleaner first and reset software. Long Term Fuel Trim Additive. Max Value, Air/Fuel too Lean.

Fault symptom

Malfunction Indicator
Lamp

The engine may stop after starting, run unevenly and misfire or run
at high rpm.


On-board diagnosis

Type of
diagnosis:

Continuous

Enable criteria:

The engine has started and lambda control is active.An additive adaptation is
carried out.Cooling and intake air temperature 60°C.Fuel level at least
12%.

Fault criteria:

The additive adaptation factor is greater than 5.25%.

Diagnostic help

Diagnosis
regards:

Checking air/fuel ratio. With this DTC, the engine will be getting too much air or too little fuel.IMPORTANTA crankcase ventilation leak may be one reason as to why a DTC is set. Check crankcase ventilation function before starting regular troubleshooting.

Functions in the diagnostic
tool related to the fault:

Test value:
•O2S1 lambda
•Additive
Adaptation
•Short Term Fuel Trim
•Purge Adaptation
•Airmass Deviation
from Calculated
•Total Fuel Trim Here's a helpful link for you: http://repairpal.com/OBD-II-Code-P0171-and-P0174


You most likely have a vac leak. Hope this helps Fix Ya! Show some love with positive feedback if this brings you to a solution. Thanks Happy Hanna-kwanz-mas

Code 51 is ( Right Rear Fuel System Lean ) A lean air/fuel mixture has been indicated by an abnormally rich correction factor. Did you get this code by the flashing check engine light?

o2 sensor: or you have stopped up injectors or a vaccum leak or egr valve sticking

Your diagnostic about this CODE is:

Generic P-Code DRB Scan Tool Display Brief Description of DTC
P0171 (M) 1/1 Fuel System Lean A lean air/fuel mixture has been indicated by an abnormally rich correction factor.
P0320 (M) No Crank Reference Signal at PCM No reference signal (crankshaft position sensor) detected during engine cranking. P0320 (M) No RPM Signal to PCM (Crankshaft Position Sensor Signal to JTEC) A CKP signal has not been detected at th
For more details, you can visit the obd_dtc_jeep

Good luck, and rated this help.

Hmmm.. Your van has No carburator.. Its direct multiport fuel injection.. It sounds like you have excessive moisture in the tank and lines.. Id try a new fuel filter..