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Chrysler Town, Dodge Caravan. Manual - part 625

Symptom:

P0172-FUEL SYSTEM 1/1 RICH

When Monitored and Set Condition:

P0172-FUEL SYSTEM 1/1 RICH

When Monitored:

With the engine running in closed loop mode, the ambient/battery

temperature above 20°F(-7°C) and altitude below 8500 ft.

Set Condition:

If the PCM multiplies short term compensation by long term adaptive and

a purge fuel multiplier and the result is below a certain value for 30 seconds over 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

TEST

ACTION

APPLICABILITY

NOTE: Check for contaminates that may have damaged the O2 Sensor:
contaminated fuel, unapproved silicone, oil and coolant.
Ignition on, engine not running.
With the DRBIII

t, read DTCs and record the related Freeze Frame data.

Is the Good Trip Counter displayed and equal to zero?

All

Yes

→ Go To 2

→ Refer to the INTERMITTENT CONDITION symptom in the

Driveability category.
Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

308

DRIVEABILITY - NGC

TEST

ACTION

APPLICABILITY

Warning: The fuel system is under a constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
Install a fuel pressure gauge.
Ignition on, engine not running.
With the DRBIII

t, actuate the ASD Fuel System test and observe the fuel pressure

gauge.
NOTE: Fuel pressure specification is 400 KPa +/- 34 KPa (58 psi +/- 5 psi).
Turn the ignition off.
Choose a conclusion that best matches your fuel pressure reading.

All

Within Specification

Go To

Above Specification

Replace the fuel filter/pressure regulator.
Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

Caution: Stop All Actuations.

NOTE: If one of the O2 Sensors Signal or Return circuits are shorted to
ground or voltage, all the other O2 Sensor voltage readings will be affected.
NOTE: After the repairs have been made, verify proper O2 Sensor operation.
If all the O2 Sensor voltage readings have not returned to normal, follow the
diagnostic procedure for the remaining O2 Sensors.
Start the engine.
Allow the engine to reach normal operating temperature.
With the DRBIII

t, read the O2 Sensor voltage.

Is the voltage switching between 2.5 and 3.4 volts?

All

Yes

→ Go To 4

→ Go To 9

Turn the ignition off.
NOTE: Allow the O2 Sensor to cool down before continuing the test. The O2
voltage should stabilize at 5.0 volts. Raising the hood may help in reducing
under hood temps.
Ignition on, engine not running.
With the DRBIII

t, actuate the O2 Heater Test.

With the DRBIII

t, monitor O2 Sensor voltage for at least 2 minutes.

Does the voltage stay above 4.5 volts?

All

Yes

→ Replace the O2 Sensor.

Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

→ Go To 5

Turn the ignition off.
Disconnect the hoses at the Evap Purge Solenoid.
Using a hand vacuum pump, apply 10 inches of vacuum to the Evap Purge Solenoid
vacuum source port on the component side.
Did the Evap Purge Solenoid hold vacuum?

All

Yes

→ Go To 6

→ Replace the EVAP Purge Solenoid.

Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

309

DRIVEABILITY - NGC

P0172-FUEL SYSTEM 1/1 RICH —

Continued

TEST

ACTION

APPLICABILITY

Turn the ignition off.
Connect a Vacuum Gauge to a Manifold Vacuum source.
Start the engine.
Allow the engine to idle.
Note: If engine will not idle, maintain a constant RPM above idle.
With the DRBIII

t in Sensors, read the MAP Sensor vacuum value.

Is the DRB reading within 1

9 of the Vacuum Gauge reading?

All

Yes

→ Go To 7

→ Replace the MAP Sensor.

Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

Note: For this test to be valid, the thermostat must be operating correctly.
Note: This test works best if performed on a cold engine (cold soak)
Ignition on, engine not running.
With the DRBIII

t, read the Engine Coolant Temperature Sensor value. If the engine

was allowed to sit overnight (cold soak), the temperature value should be a sensible
value that is somewhere close to the ambient temperature.
Note: If engine coolant temperature is above 82°C (180°F), allow the engine
to cool until 65°C (150°F) is reached.
Start the Engine.
During engine warm-up, monitor the Engine Coolant Temperature value. The temp
value change should be a smooth transition from start up to normal operating temp
82°C (180°F). The value should reach at least 82°C (180°F).
Did the Engine Coolant Temperature value increase a smooth transition and did it
reach at least 82°C

All

Yes

→ Go To 8

→ Replace the Engine Coolant Temperature Sensor.

Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

Check for any of the following conditions/mechanical problems.
AIR INDUCTION SYSTEM - must be free from restrictions.
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
ENGINE PCV SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
FUEL INJECTOR - plugged or restricted injector; control wire not connected to
correct injector
Are there any engine mechanical problems?

All

Yes

→ Repair as necessary.

Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

→ Test Complete.

310

DRIVEABILITY - NGC

P0172-FUEL SYSTEM 1/1 RICH —

Continued

TEST

ACTION

APPLICABILITY

Ignition on, engine not running.
Disconnect the O2 Sensor harness connector.
With the DRBIII

t, monitor the O2 Sensor voltage.

The O2 Sensor voltage should read 5.0 volts on the DRBIII

t with the connector

disconnected.
Using a jumper wire, jump from the O2 Signal circuit to the O2 Return circuit in the
O2 Sensor harness connector.
NOTE: The voltage should drop from 5.0 volts down to 2.5 volts with the
jumper wire connected.
Did the O2 Sensor voltage drop from 5 volts to 2.5 volts?

All

Yes

→ Replace the O2 Sensor

Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

→ Go To 10

Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Turn the ignition on.
Measure the voltage of the O2 Signal circuit in the O2 Sensor harness connector.
Is the voltage above 4.8 volts?

All

Yes

→ Check the O2 Signal circuit for damage, short to ground, open, or

short to voltage. Inspect the O2 Sensor connector and the PCM
harness connector. If OK, replace the Powertrain Control Module
in accordance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

→ Go To 11

Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Turn the ignition on.
Measure the voltage on the O2 Return circuit in the O2 Sensor harness connector.
Is the voltage at 2.5 volts?

All

Yes

→ NOTE: Before continuing, check the PCM harness connector

terminals for corrosion, damage, or terminal push out. Repair as
necessary. Replace and program the Powertrain Control Module
in accordance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 5 - NGC.

→ Check the O2 Return circuit for damage, short to ground, open, or

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DRIVEABILITY - NGC

P0172-FUEL SYSTEM 1/1 RICH —

Continued

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