Diagnostic Aids

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Any unmetered air that enters the engine downstream of the MAF sensor may cause this DTC to set.
A short between the signal circuit of the MAF sensor and the signal circuit of the intake air temperature (IAT) sensor will skew the MAF sensor higher than normal at idle and less than normal at higher air flows.
A malfunctioning MAF sensor can cause excessive engine emissions.
The MAF display should increase from 24-50 g/s at idle to 320 g/s or more at the 2-3 shift during a wide-open throttle (WOT) acceleration. If not, inspect for a restriction in the induction system or the exhaust system.
If the vehicle condition is intermittent, refer to Inducing Intermittent Fault Conditions and Intermittent Conditions .

DTC P0101

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Engine Controls?	-	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Review the DTC information on the scan tool. Is DTC P0405 set?	-	Go to DTC P0405	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. 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 4	Go to Diagnostic Aids
4	Turn OFF the ignition. Turn ON the ignition, with the engine OFF. Observe the MAF Sensor parameter with a scan tool. Is the MAF Sensor parameter more than the specified value?	0.30 V	Go to Step 7	Go to Step 5
5	Turn OFF the ignition. Inspect for air leaks in the following components: The air induction system and the turbocharger system The charge air cooler with a J 46091 Charge Air Cooler Tester The mass air flow (MAF)/intake air temperature (IAT) sensor O-ring seal The boost pressure sensor seal An exhaust gas recirculation (EGR) valve gasket that is missing or damaged Inspect for the following conditions: A cracked MAF sensor housing An obstructed intake air duct or a dirty air filter element Any debris that is blocking the air sensing filaments of the MAF sensor Any water intrusion in the air induction system A MAF sensor that is installed backwards An EGR valve that is sticking-Refer to Exhaust Gas Recirculation (EGR) System Cleaning . A restricted exhaust system-Refer to Restricted Exhaust . Did you find and correct the condition?	-	Go to Step 24	Go to Step 6
6	Turn ON the ignition, with the engine OFF. Observe both the BARO parameter and the Boost Pressure Sensor parameter with a scan tool. Is the difference between the sensors equal to or less than the specified value?	5 kPa	Go to Step 8	Go to DTC P2227
7	Disconnect the MAF/IAT sensor. Observe the MAF Sensor parameter with a scan tool. Is the MAF Sensor parameter more than the specified value?	0 V	Go to Step 14	Go to Step 8
8	Connect the MAF/IAT sensor. Start the engine and allow it to idle. Observe the MAF Sensor parameter with a scan tool. Move the harness and the connector of the MAF/IAT sensor. Does the movement of the harness or the connector affect the MAF Sensor parameter?	-	Go to Step 21	Go to Step 9
9	Turn OFF the engine. Turn ON the ignition, with the engine OFF. Measure the battery voltage with a DMM. Disconnect the MAF/IAT sensor. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Refer to Probing Electrical Connectors and Circuit Testing . Connect the DMM to the probe of the test lamp and a good ground. Refer to Measuring Voltage Drop and Circuit Testing . Is the voltage within 1.5 volts of the specified value?	B+	Go to Step 10	Go to Step 18
10	IMPORTANT: All electrical components and accessories must be turned OFF. Turn OFF the ignition for 60 seconds to allow the control modules to power down before proceeding. Measure the resistance from the low reference circuit of the MAF sensor to a good ground with a DMM. Refer to Circuit Testing . Is the resistance less than the specified value?	5 ohm	Go to Step 11	Go to Step 12
11	Turn ON the ignition, with the engine OFF. Connect a 3-amp fused jumper wire between the signal circuit of the MAF sensor and the signal circuit of the IAT sensor. Refer to Circuit Testing . Observe the MAF Sensor parameter with a scan tool. Is the MAF Sensor parameter more than the specified value?	445 g/s	Go to Step 16	Go to Step 13
12	Disconnect the engine control module (ECM). Test the MAF sensor low reference circuit for the following conditions: A high resistance An intermittent open Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	-	Go to Step 24	Go to Step 17
13	Turn OFF the ignition. Disconnect the ECM. Test the MAF sensor signal circuit for the following conditions: A high resistance or an intermittent open A high resistance short to ground A high resistance short to the low reference circuit of the MAF sensor or the IAT sensor Refer to Inducing Intermittent Fault Conditions and Circuit Testing and Wiring Repairs . Did you find and correct the condition?	-	Go to Step 24	Go to Step 17
14	IMPORTANT: Disconnecting the ECM connectors may eliminate the short to voltage if the signal circuit is shorted to another ECM circuit. Turn OFF the ignition. Disconnect the ECM, C1 connector only. Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the MAF sensor to a good ground with a DMM. Refer to Circuit Testing . Is the voltage more than the specified value?	0 V	Go to Step 19	Go to Step 15
15	Turn OFF the ignition. Disconnect all of the ECM connectors. Measure the resistance from the signal circuit of the MAF sensor to all other circuits at all ECM connectors with a DMM. Refer to Circuit Testing . Is the resistance less than the specified value?	infinity ohm	Go to Step 20	Go to Step 17
16	Test for shorted terminals, an intermittent and for a poor connection at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs . Did you find and correct the condition?	-	Go to Step 24	Go to Step 22
17	Test for shorted terminals, an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals and Connector Repairs . Did you find and correct the condition?	-	Go to Step 24	Go to Step 23
18	Repair the high resistance or the intermittent open in the MAF sensor ignition 1 voltage circuit. Refer to Wiring Repairs . Did you complete the repair?	-	Go to Step 24	-
19	Repair the short to voltage in the MAF sensor signal circuit. Refer to Wiring Repairs . Did you complete the repair?	-	Go to Step 24	-
20	Repair the circuits that are shorted together. Refer to Wiring Repairs s. Did you complete the repair?	-	Go to Step 24	-
21	Repair the harness or the connections as necessary. Refer to Connector Repairs , Repairing Connector Terminals , and Wiring Repairs . Did you complete the repair?	-	Go to Step 24	-
22	Replace the MAF/IAT sensor. Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement . Did you complete the replacement?	-	Go to Step 24	-
23	Replace the ECM. Refer to Engine Control Module (ECM) Replacement . Did you complete the replacement?	-	Go to Step 24	-
24	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 25
25	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List	System OK