For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P0315: Mass Air Flow (MAF) Sensor Circuit Low Frequency

### Circuit Description

The crankshaft position (CKP) system variation learn feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft, and the CKP sensor. The calculated error allows the engine control module (ECM) to accurately compensate for reference period variations. This enhances the ability of the ECM to detect misfire events over a wider range of engine speed and load.

The CKP system variation compensating values are stored in ECM memory after a learn procedure has been performed and the ignition switch is turned to OFF for at least 30 seconds. If the actual CKP variation is not within the CKP system variation compensating values stored in the ECM, DTC P0300 may set.

If the CKP system variation values are not stored in the ECM memory, or a proper ECM power down does not occur after completing the CKP Learn Procedure, DTC P0315 is set.

### Conditions for Running the DTC

• | The PCM is in running state.

• | Fault Counter has been reset to 0.

• | This diagnosis runs continuously.

### Conditions for Setting the DTC

The ECM detects that the CKP system variation values are not stored in memory.

### Action Taken When the DTC Sets

DTC P0315 is a Type A DTC.

### Conditions for Clearing the DTC

DTC P0315 is a Type A DTC.

### Diagnostic Aids

• | A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 1.5 g/s at idle to 380 g/ s or more at the time of the 1-2 shift.

• | Verify that any electrical aftermarket devices are properly connected and grounded. Refer to Checking Aftermarket Accessories .

### Reference Information

#### DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Engine Control Module Scan Tool Information

### Circuit/System Testing

Important: The CKP system variation learn procedure may have to be repeated up to 5 times before the procedure is learned.

1. Perform the Crankshaft Position System Variation Learn. If the scan tool displays Learned This Ignition.
2. If the CKP System Variation Learn Procedure cannot be performed successfully, inspect for the following conditions:

• | Any worn crankshaft main bearings

• | A damaged or misaligned reluctor wheel

• | Excessive crankshaft runout

• | Crankshaft damaged--Refer to Crankshaft and Bearing Cleaning and Inspection .

• | Interference in the signal circuit of the CKP sensor

• | The ignition switch is in the ON position until there is insufficient system voltage

• | An ECM power disconnect with the ignition ON that may have erased the CKP system variation values and set DTC P0315.

• | Debris between the CKP sensor and the reluctor wheel

⇒ | If the control module is unable to complete the learn procedure, replace the control module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming