P0721

Diagnostic Chart:

Wiring Diagram:

Speed signal noise is an irregularity in the normal stream of vehicle speed signal pulses. There are three conditions that are identified as noise: Missing pulses in a revolution of the differential housing, extra pulses in a revolution of the differential housing, slow pulses.

DTC PARAMETERS

DTC P0721 is set when the PCM has seen the following conditions for one second twice per ignition cycle.

- Vehicle speed noise DTCs set. Parameter status = yes.

- Vehicle speed is greater than 24 km/h (15 mph).

- Condition exists for 0.7 seconds.

TEST DESCRIPTION

Numbered steps below refer to numbered steps on chart.

1. This test checks PCM connector for open, spread, corroded terminals or loose wires.

2. This test checks PCM for internal intermittent faults.

3. This test checks vehicle speed sensor (VSS) connector for open, spread, corroded terminals or loose wires.

4. This step is a visual inspection of the VSS connector and the PCM connector to check for open, spread or corroded terminals.

5. This step checks for secondary ignition wires routed close to VSS circuits 400 and 401 and other potential causes.

REPAIR VERIFICATION

Monitor DTC menu "Code Status" for "Pass Since Code Clear" and "Pass This Ignition Cycle." When both have passed, repair is verified.

Criteria for pass:

- Output speed greater than 24 km/h (15 mph).

- No noise for greater than 0.5 seconds,

DIAGNOSTIC AIDS

When attempting to diagnose an intermittent problem use the Scan tool* to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem.

* Select MALF History and DTC status from DTC menu of Scan tool.

Check the tightness of the female terminal grip with a spare male terminal.

Check wire routing for possible chafed wires.