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.

Inspect for the following conditions:

Any unmetered air-Any unmetered air that enters the engine downstream of the MAF sensor may cause this DTC to set.
A sluggish or unresponsive MAF sensor-A short between the signal circuit of the MAF sensor and the signal circuit of the intake air temperature (IAT) sensor. This will cause the MAF sensor to have a very limited output voltage range.
A malfunctioning MAF sensor can cause excessive engine emissions.
An open on the 5-volt reference circuit of the barometric pressure (BARO) sensor may cause this DTC to set.
A short to ground on the signal circuit of the BARO sensor may cause this DTC to set.
The signal circuit of the BARO sensor shorted to 5 volts may cause this DTC to set.
An open signal circuit of the BARO sensor may cause this DTC to set.
The MAF display should increase from 42-50 g/s at idle to 420 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 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	Start the engine Monitor the Diagnostic Trouble Code (DTC) Information using the scan tool. Does the scan tool display any other DTCs set?	-	Go to Diagnostic Trouble Code (DTC) List	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	Inspect the fuse in the ignition 1 voltage circuit of the mass air flow (MAF) sensor. Is the fuse open?	-	Go to Step 17	Go to Step 5
5	Turn OFF the ignition. Inspect for air leaks in the following components: A damaged MAF Sensor housing The air induction system and the turbocharger system The charge air cooler with a J 46091 Charge Air Cooler Tester The MAF sensor O-ring seal The boost pressure sensor seal The exhaust gas recirculation (EGR) throttle valve solenoid, diaphragm, or vacuum hose The EGR valve solenoid valve diaphragm, or vacuum hose The EGR vent solenoid or vacuum hose Inspect for the following conditions: Any kinks or restrictions in any of the EGR solenoid vacuum hoses 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 A restricted exhaust system-Refer to Restricted Exhaust in Engine Exhaust. Did you find and correct the condition?	-	Go to Step 26	Go to Step 6
6	Turn ON the ignition, with the engine OFF. Observe both the BARO kPa and the boost pressure sensor kPa with a scan tool. Is the difference between the sensors equal to or less than the specified value?	4 kPa	Go to Step 7	Go to DTC P2227 (Federal RPO FE9, NG1) or DTC P2227 (California RPO YF5, NE1, and VCL)
7	Start the engine and allow the engine to idle. Observe the MAF Sensor g/s with a scan tool. Move the harness and the connector of the MAF sensor. Does the movement of the harness or the connector affect the MAF sensor g/s?	-	Go to Step 21	Go to Step 8
8	Observe the MAF Sensor parameter with a scan tool. Is the MAF Sensor parameter less than the specified value?	16 g/s	Go to Step 11	Go to Step 9
9	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 10	Go to Step 11
10	Disconnect the harness connector of the MAF sensor. Is the MAF Sensor parameter more than the specified value?	445 g/s	Go to Step 15	Go to Step 11
11	Turn OFF the engine. Turn ON the ignition, with the engine OFF. Disconnect the harness connector of the MAF sensor. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Refer to Circuit Testing in Wiring Systems. Does the test lamp illuminate?	-	Go to Step 12	Go to Step 17
12	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. Measure the resistance from the ground circuit of the MAF sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the resistance less than the specified value?	5 ohm	Go to Step 13	Go to Step 18
13	Turn ON the ignition, with the engine OFF. Connect a 3-amp fused jumper wire between the signal circuit of the intake air temperature (IAT) sensor and the signal circuit of the MAF sensor. Observe the MAF sensor parameter with a scan tool. Is the MAF sensor value more than the specified value?	445 g/s	Go to Step 22	Go to Step 14
14	Turn OFF the ignition. Disconnect the fused jumper wire. Disconnect the engine control module (ECM). Test the signal circuit between the ECM and the MAF sensor for the following conditions: A high resistance or an open A short to ground A short to the low reference circuit of the MAF sensor or IAT sensor-Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 26	Go to Step 16
15	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. Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Refer to Circuit Testing in Wiring Systems. Is the voltage near the specified value?	0 V	Go to Step 16	Go to Step 19
16	Test for continuity at the harness connector of the ECM from the signal circuit of the MAF sensor to all other circuits at both ECM connectors with a DMM. Refer to Circuit Testing in Wiring Systems. Does the DMM indicate continuity between any other circuit?	-	Go to Step 20	Go to Step 23
17	Repair the short to ground or an open in the ignition 1 voltage circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Replace the fuse if necessary. Did you complete the repair?	-	Go to Step 26	Go to Step 24
18	Repair the high resistance or an open in the low reference circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	-	Go to Step 26	Go to Step 23
19	Repair the short to voltage in the signal circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	-	Go to Step 26	-
20	Repair the circuits that are shorted together. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	-	Go to Step 26	-
21	Repair the harness or the connections as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	-	Go to Step 26	-
22	Inspect for poor connections at the harness connector of the MAF sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 26	Go to Step 24
23	Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 26	Go to Step 25
24	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 26	-
25	Replace the ECM. Refer to Engine Control Module (ECM) Replacement . Did you complete the Replacement?	-	Go to Step 26	-
26	With a scan tool clear the DTCs. 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 27
27	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