DTC P1171 Fuel System Lean During Acceleration. Chevrolet Caprice 1996

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1996 🢒 Caprice 🢒 Engine 🢒 Engine Controls - 4.3L (Caprice Only) and 5.7L 🢒 DTC P1171 Fuel System Lean During Acceleration

Circuit Description

The PCM can identify if the vehicles fuel system is capable of supplying adequate amounts of fuel during heavy acceleration (power enrichment).When the power enrichment mode of operation is requested during Closed Loop operation (by heavy acceleration), the PCM will provide more fuel to the engine. Under these conditions, the PCM should detect a rich condition.

Conditions for Setting the DTC

•	DTCs P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0410, P0412, P1112, P1114, P1121, P1153, P1155 not set.

•	The engine is operating in Closed Loop.

•	Not in fuel cut off mode.

•	The PCM detects lean oxygen sensor voltage for 3 seconds during power enrichment mode.

Action Taken When the DTC Sets

•	The DTC will be stored in the PCM memory when the diagnostic runs and fails.

•	The Malfunction Indicator Lamp (MIL) will not illuminate.

•	The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in Failure Records.

Conditions for Clearing the MIL/DTC

•	A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

•	A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.

•	PCM battery voltage is interrupted.

•	Using a scan tool.

Diagnostic Aids

•	A restricted fuel filter can supply adequate amounts of fuel at idle but may not be able to supply enough fuel during heavy acceleration. A vapor lock condition can also set this DTC.

•	If it is not possible to cause this DTC to re-set, it may have been caused by the customer running the vehicle out of fuel.

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Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that were noted. This will isolate when the DTC failed.

For intermittents, refer to Symptoms .

Test Description

Number(s) below refer to step numbers on the diagnostic table.

Wrap a shop towel around the fuel pressure connector to absorb any small amount of fuel leakage that may occur when installing the gauge. With the ignition ON, pump pressure should be 284-325 kPa (41-47 psi). This pressure is controlled by spring pressure within the regulator assembly. Pressure below 284 kPa (41 psi) may cause hard starting cold and poor driveability. Low enough pressure will cause the engine not to run at all. Restricted flow may allow the engine to run at idle, or at low speeds, but may cause a surge and stall when more fuel is required, as when accelerating or driving at high speeds. Low fuel pressure under heavy acceleration conditions may set this DTC.

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

If any HO2S DTC is set, go to that table first.
Install Fuel Pressure Gauge J 34730-1. Refer to Fuel System Diagnosis .
Ignition OFF for 10 seconds, A/C OFF.
Turn the ignition ON. The fuel pump will run for about 2 seconds. It may be necessary to cycle the ignition ON more than once to obtain maximum pressure.
Note fuel pressure with pump running. Pressure should be within the range shown. When the pump stops, the pressure may vary slightly then should hold steady.

Is the pressure correct and does it hold?

284-325 kPa (41-47 psi)

Go to Step 3

Go to Fuel System Diagnosis

Check for the following conditions:

•	Restricted in-line fuel filter.

•	Restricted/damaged fuel pressure line.

•	Restricted/clogged fuel pump strainer.

Was a problem found and corrected?

Go to Step 5

Go to Step 4

Replace faulty fuel pump.

Is the action complete?

Go to Step 5

Using the scan tool, select DTC, Clear Info.
Start the engine and idle at normal operating temperature.
Select DTC, Specific, then enter the DTC number which was set.
Operate the vehicle within the conditions for setting this DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

Go to Step 6

Go to Step 2

Using the scan tool, select Capture Info, Review Info.

Are any DTCs displayed that have not been diagnosed?

Go to the applicable DTC table

System OK