MAS Super charger and bad gas
 

I have and 03 H2 with a Magna Charger on it. I put 84 oct. in it and the check engine light came on. I called onstar to run a system diagnostic. They would not give me the code , but said it was the engine fuel control system. I then took it up to the neighborhood AutoZone and they said it was p1074 twice which usually means that it is the MAS. Would bad gas or low octane cause this ? I'm Leary to take it back to the dealer since my extended warranty got voided because of the super charger. I had to replace my transmission and was thinking maybe a loose vacuum hose might be causing it.

Thanks for the help.

Re: MAS Super charger and bad gas
 

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor (O2S) input. During Closed Loop, the O2S inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the O2S indicate a lean condition, fuel trim values will be above 0 percent. If the O2S indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, DTC P0171 or P0174 sets.
Conditions for Running the DTC


.
Conditions for Setting the DTC

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

Diagnostic Aids

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. If conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
2. If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

Step
Action
Values
Yes
No
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Important: If any DTCs other than P0171 or P0174 are set, refer to those DTCs before continuing

1. <LI type=1>Install the scan tool. <LI type=1>Start and idle the engine at the normal operating temperature in Closed Loop. <LI type=1>Record the long term fuel trim. <LI type=1>Turn OFF the engine. <LI type=1>Turn ON ignition, with engine OFF.
2. 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?
23%
Go to Step 3
Go to Diagnostic Aids
3

1. <LI type=1>Operate engine at idle.
2. 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 4
Go to Step 5
4
Turn OFF the engine.

1. 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 tank. If fuel pressure is too low this DTC may set. Refer to. Fuel System Diagnosis
   - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis

Did you find and correct the condition?
--
Go to Step 7
Go to Step 6
5

1. <LI type=1>Turn OFF the engine. <LI type=1>Inspect the HO2S for proper installation. <LI type=1>Verify the electrical connectors and the wires are secure, and not contacting the exhaust system.
2. Test for continuity between the HO2S signal circuit and the low reference circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 7
Go to Fuel System Diagnosis
6

1. <LI type=1>Operate the engine at idle. <LI type=1>Inspect for any missing, loose, or leaking exhaust components forward of the HO2S. <LI type=1>Inspect for vacuum leaks at the intake manifold, throttle body, and injector O-rings. <LI type=1>Inspect the air induction system and the air intake ducts for leaks. <LI type=1>Inspect the secondary air injection (AIR) system for leaks, improper air delivery, and for the shut-off valves not closing.
2. Inspect the crankcase ventilation system for leaks. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.

Did you find and correct the condition?
--
Go to Step 7
Go to Symptoms - Engine Mechanical in Engine Mechanical
7
Important: After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.

1. <LI type=1>Clear the DTCs with a scan tool. <LI type=1>Turn OFF the ignition for 30 seconds. <LI type=1>Start the engine.
2. 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