Diagnostic Aids

WARNING: This page is about a different car, the 2007 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.

The 5.3L engine, VIN code Z, may use either 100% pure unleaded fuel or unleaded fuel containing up to 85% ethanol, or E85. Refer to Fuel System Description . This DTC can set if the learned alcohol content is not within 15% of the actual alcohol content in the fuel tank. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool and without E85) or Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) .
Excessive resistance in the fuel injector control and/or the ignition 1 voltage circuits may cause the following symptoms:
- Misfire
- Rough idle
  Refer to DTC P0200 .
The system may become lean if an injector is not supplying enough fuel.
A lean condition could be present during high fuel demand.
Review the Failure Records with a scan tool. If an intermittent condition is suspected, refer to Testing for Intermittent Conditions and Poor Connections .

DTC P0171 or P0174

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Are any DTCs other than DTC P0171 or P0174 also set?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Step 3
3	Install the scan tool. Start and idle the engine at the normal operating temperature in Closed Loop. Record the long term fuel trim. Turn OFF the engine. Turn ON ignition, with the engine OFF. Review the Freeze Frame/Failure Records and record the displayed data for this DTC. Does the scan tool indicate that the long term fuel trim is greater than the specified value?	24%	Go to Step 4	Go to Diagnostic Aids
4	Operate the engine at idle. Observe the HO2S parameters with a scan tool. Does the scan tool indicate that the parameter is within the specified range and fluctuating?	200-800 mV	Go to Step 5	Go to Step 6
5	Turn OFF the engine. Visually and physically inspect the following items: The vacuum hoses for splits, kinks, and proper connections-Refer to Emission Hose Routing Diagram . Ensure that the vehicle has sufficient fuel in the tank. If the fuel pressure is too low, this DTC may set. Refer to Fuel System Diagnosis . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool and without E85)Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) . Any lean fuel injectors-Refer to Fuel Injector Balance Test with Tech 2 . Did you find and correct the condition?	-	Go to Step 8	Go to Step 7
6	Turn OFF the engine. Inspect the heated oxygen sensor (HO2S) for proper installation. Verify the electrical connectors and the wires are secure, and not contacting the exhaust system. Test for continuity between the HO2S signal circuit and the low reference circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	-	Go to Step 8	Go to Fuel System Diagnosis
7	Operate the engine at idle. Inspect for any missing, loose, or leaking exhaust components forward of the HO2S. Inspect for vacuum leaks at the intake manifold, throttle body, and injector O-rings. Inspect the air induction system and the air intake ducts for leaks. Inspect the secondary air injection (AIR) system for leaks, improper air delivery, and for the shut-off valves not closing. Inspect the crankcase ventilation system for leaks. Refer to Crankcase Ventilation System Inspection/Diagnosis . The evaporative emission (EVAP) lines and components for damage or blockage-Refer to Evaporative Emissions Hose Routing Diagram . Inspect the vacuum brake booster for leaks. Did you find and correct the condition?	-	Go to Step 8	Go to Symptoms - Engine Mechanical
8	IMPORTANT: After repairs, use the scan tool Fuel Trim Reset function to reset the Long Term Fuel Trim. Turn ON the ignition, with the engine OFF. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	-	Go to Step 2	Go to Step 9
9	In order to ensure that the performance of the catalyst has not been affected by the fault that set this DTC, operate the vehicle within the conditions for running and setting DTC P0420 or P0430 and verify that P0420 or P0430 runs and passes. Refer to DTC P0420 or P0430 . Does the DTC run and pass?	-	Go to Step 10	Go to DTC P0420 or P0430
10	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	System OK