DTC P1171 Fuel System Lean During Acceleration. GMC Truck Sonoma Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 Sonoma Pickup - 2WD 🢒 DTC 🢒 DTC P1171 Fuel System Lean During Acceleration


(1)	Fuel Pressure Regulator
(2)	Fuel Shut Off Adapter J 37287
(3)	Fuel Return Line
(4)	Quick Connect Adapter
(5)	Fuel Pressure Pinch Point
(6)	Fuel Pressure Pinch Point
(7)	Fuel Pressure Gauge Kit J 29658-D
(8)	Fuel Filter
(9)	Fuel Pressure Line

Circuit Description

The PCM's internal circuitry can identify if the vehicle fuel system is capable of supplying adequate amounts of fuel during heavy acceleration (power enrichment). When a power enrichment mode of operation is requested during a Closed Loop operation (by heavy acceleration), the PCM provides additional fuel to the engine. Under these conditions the PCM should detect a rich condition. Whenever this rich exhaust is not detected, a DTC P1171 sets. A plugged fuel filter or restricted fuel line can prevent adequate amounts of fuel from being supplied during power enrichment mode.

Conditions for Running the DTC

•	No active Oxygen Sensor DTC's

•	The engine coolant temperature is more than 20°C (70°F).

•	The engine has been running for longer than 20 seconds.

•	The engine is operating in a Closed Loop operation.

Conditions for Setting the DTC

•	The O2S 1 voltage is less than 300 mV for 5 seconds.

•	The engine is in the power enrichment mode.

Action Taken When the DTC Sets

•	The PCM records the operating conditions at the time the diagnostic fails. The Failure Records buffers stores this information.

•	A history DTC is stored.

Conditions for Clearing the DTC

•	A History DTC clears after 40 consecutive warm up cycles without a fault.

•	Use a scan tool to clear the DTCs.

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. Water or alcohol in the fuel may cause low O2S 1 voltage during acceleration.

•	Check for faulty or plugged fuel injectors.

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when this DTC sets. The scan tool stores this data for later reference.

This step checks to see if the O2S 1 is operating properly.

If no malfunctions are present at this point and no additional DTCs were set, refer to the Diagnostic Aids for additional checks and information.

Step	Action	Value(s)	Yes	No
1	Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Turn ON the ignition leaving the engine OFF. Install a scan tool. Are any component related DTCs set?	--	Go to applicable DTC table	Go to Step 3
3	Check the vehicle for an adequate amount of fuel. Add fuel to the vehicle's fuel tank if the tank is almost empty. Was it necessary to add fuel?	--	Go to Step 5	Go to Step 4
4	Start the engine. Run the engine at the specified temperature and RPM. Observe the O2S 1 voltage with the scan tool. The O2S 1 voltage should vary from the specified voltage and occasionally toggle above the specified voltage. Does the O2S 1 toggle?	75°C - 95°C (167°F - 203°F) 1,200 RPM 100 - 900 mV 447 mV	Go to Fuel System Diagnosis	Go to DTC P0134 O2S Circuit Insufficient Activity Sensor 1
5	Using the scan tool, clear the DTCs. Start the engine. Idle the engine at the normal operating temperature. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text. Does the scan tool indicate that this diagnostic has ran and passed?	--	Go to Step 6	Go to Step 2
6	Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed?	--	Go to the applicable DTC table	System OK