HY: Generator/Regulator System

HY: Introduction See: HY: Generator/Regulator System - Introduction

HY1 DTC P1246: VERIFY GENERATOR DRIVE FUNCTION

• Check generator drive belt condition.
• Check generator drive belt tension.
• Start engine, verify generator turning.

Does generator turn?
Yes

• GO to HY2

.

No

• REFER to Charging System.

HY2 VERIFY CHARGING SYSTEM IS EEC CONTROLLED

• Key off.
• Disconnect battery terminals at battery, and the battery lead to the alternator.
• Disconnect generator harness connector and measure resistance between battery-sense and gen-com pin at the generator.

Is resistance between 950 and 1050 ohms?
Yes

• GO to HY3

.

No

• REPLACE generator/regulator assembly.

HY3 CHECK BATTERY-SENSE VOLTAGE AT BATTERY

• Note: When checking voltage of the battery sense circuit at the alternator, it may be necessary to clean and or tighten the connector nut.
• Reconnect generator.
• Reconnect battery.

Is battery voltage at battery-sense circuit pin at the generator/regulator harness connector within plus or minus 0.5 volt of battery voltage?
Yes

• GO to HY4

.

No

• REPAIR battery-sense circuit.

HY4 CHECK GENERATOR FAILURE MODE

• All electrical load off.
• Access the GFSF PID.
• Increase engine speed to 2,000 rpm.
• Perform wiggle test.

Is a failure indicated?
Yes

• GO to HY5

.

No

• REFER to Charging System.

HY5 CHECK GEN-MON AND GEN-COM CIRCUIT FOR SHORT TO POWER

• Key off.
• PCM and generator/regulator disconnected.
• Key on.
• Measure voltage between gen-com signal pin at the PCM harness connector and chassis ground.
• Measure voltage between gen-mon signal pin at the PCM harness connector and chassis ground.

Is each voltage greater than 0.5 volt?
Yes

• KEY OFF. REPAIR short circuit.

No

• KEY OFF. GO to HY6

.

HY6 CHECK GEN-MON AND GEN-COM CIRCUIT FOR SHORT TO GROUND

• Measure resistance between the gen-com signal pin at the PCM harness connector and chassis ground.
• Measure resistance between the gen-mon signal pin at the PCM harness connector and chassis ground.

Is resistance greater than 10,000 ohms?
Yes

• GO to HY7

.

No

• REPAIR short circuit.

HY7 CHECK GEN-MON AND GEN-COM CIRCUIT FOR OPEN

• Measure resistance of the gen-com circuit between the generator/regulator harness connector and the PCM harness connector.
• Measure resistance of the gen-mon circuit between the generator/regulator connector and the PCM harness connector.

Is each resistance less than 5.0 ohms?
Yes

• GO to HY8

.

No

• REPAIR open circuit.

HY8 CHECK GENERATOR MONITOR SIGNAL

• Engine idling.
• Access GFS PID.

Is duty cycle between 6-98%?
Yes

• GO to HY9

.

No

• REPLACE generator/regulator assembly.

HY9 CHECK GENERATOR COMMUNICATOR SIGNAL

• Access GENFDC PID.
• Engine idling.
• Toggle load on and off (headlights).

Does PID switch within 0-99% range?
Yes

• Generator function is OK. GO to Pinpoint Test Z See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\Z: Intermittent - Introduction

,
intermittent circuit failure diagnosis.

No

• REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) See: Programming and Relearning\Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM).