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Generator/Regulator System Malfunction

DTC P0622, P1246, P1630, P1631, P1634 DETECTION CONDITION AND POSSIBLE CAUSES

DTC P0622, P1246, P1630, P1631, P1634 GENERATOR/REGULATOR SYSTEM MALFUNCTION
DETECTION CONDITION
  • P0622 and P1246 indicates the generator load input is not within a calibrated limit for a calibrated amount of time.
POSSIBLE CAUSE
  • GEN-MON circuit short to GND.
  • GEN-MON circuit short to B+.
  • GEN-MON circuit open.
  • GEN-COM circuit short to GND.
  • GEN-COM circuit short to B+.
  • GEN-COM circuit open.
  • Battery-sense circuit open.
  • Damaged voltage regulator/generator.
  • Damaged PCM.
HINT Generator/Regulator Description 
  • The generator communication (GEN COM) line communicates the desired setpoint from the PCM to the voltage regulator.
  • The generator monitor (GEN MON) line communicates the generator load and error conditions to the PCM.
  • The third circuit on the voltage regulator, the B/Y circuit, is a dedicated battery voltage sense line.
G04319023Courtesy of MAZDA MOTORS CORP.
DTC P0622, P1246, P1630, P1631, P1634 DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1
  • Was PCM Quick Test performed? 
 Yes Go to next step.
No Perform PCM Quick Test. See PCM QUICK TEST .
2 VERIFY GENERATOR DRIVE CYCLE
  • Check generator drive belt condition and tension.
  • Start engine and verify generator is turning.
  • Is everything OK? 
 Yes Go to next step.
No Repair or replace parts.
Go to step 11.
3 VERIFY CHARGING SYSTEM IS EEC CONTROLLED
  • Key OFF.
  • Disconnect battery cables at battery.
  • Disconnect generator harness connector and measure resistance between BATT-SENSE and GEN-COM pins at the generator.
  • Is resistance between 950 and 1050 ohms? 
 Yes Go to next step.
No Replace generator/regulator assembly.
GENERATOR - 2.3L or GENERATOR - 3.0L (4V) .
Go to step 11.
4 CHECK BATTERY-SENSE VOLTAGE AT BATTERY
  • Reconnect battery cables.
  • Measure voltage at generator/regulator harness connector between BATT-SENSE and chassis ground.
  • Is battery voltage of battery-sense circuit within plus or minus 0.5 volts of battery voltage? 
 Yes Go to next step.
No VERIFY the battery junction box (BJB) fuse 9 (15A) is OK. If OK, Repair BATT-SENSE circuit.
Go to step 11.
5 CHECK GENERATOR FAILURE MODE
  • Turn off all electrical loads.
  • Access GFS PID.
  • Start engine and increase engine speed to 2000 rpm.
  • Perform wiggle test.
  • Is a failure indicated? 
 Yes Go to next step.
No Repair or replace parts.
Go to step 11.
6 CHECK GEN-MON AND GEN-COM CIRCUIT FOR SHORT TO POWER
  • Key OFF.
  • Disconnect generator.
  • Disconnect PCM.
  • Install Breakout Box, leave PCM disconnected.
  • Key ON, Engine OFF (KOEO), Engine OFF.
  • Measure voltage between PCM test pin E7 (GEN-COM) and chassis ground.
  • Measure voltage between PCM test pin E16 (GEN-MON) and chassis ground.
  • Key OFF.
  • Is each voltage greater than 0.5 ohms? 
 Yes Repair short circuit.
Go to step 11.
No Go to next step.
7 CHECK GEN-MON AND GEN-COM CIRCUIT FOR SHORT TO GROUND
  • Measure resistance between PCM test pin E7 (GEN-COM) and chassis ground.
  • Measure resistance between PCM test pin E16 (GEN-MON) and chassis ground.
  • Is each resistance greater than 10K ohms? 
 Yes Go to next step.
No Repair short circuit.
Go to step 11.
8 CHECK GEN-MON AND GEN-COM CIRCUIT FOR OPEN
  • Measure resistance of GEN-COM circuit between PCM test pin E7 and generator/regulator harness connector.
  • Measure resistance of GEN-MON circuit between PCM test pin E16 and generator/regulator harness connector.
  • Is each resistance less than 5.0 ohms? 
 Yes Go to next step.
No Repair open circuit.
Go to step 11.
9 CHECK GENERATOR MONITOR SIGNAL
  • Key ON, Engine Running (KOER).
  • Access GF PID.
  • Is duty cycle between 6-98%? 
 Yes Go to next step.
No Replace generator/regulator assembly.
GENERATOR - 2.3L or GENERATOR - 3.0L (4V) .
Go to step 11.
10 CHECK GENERATOR COMMUNICATOR SIGNAL
  • Key ON, Engine Running (KOER).
  • Access GENFDC PID.
  • Toggle load on and off (headlights).
  • Is duty cycle between 0-99% range? 
 Yes Go to next step.
No Replace generator/regulator assembly.
GENERATOR - 2.3L or GENERATOR - 3.0L (4V) .
Go to step 11.
11 VERIFY TROUBLESHOOTING OF DTCs COMPLETED
  • Make sure to reconnect all disconnected connectors.
  • Clear DTCs from PCM memory using WDS or equivalent tester generic OBD II function.
  • Perform PCM Quick Test. See PCM QUICK TEST .
  • Is any DTC present? 
 Yes Replace PCM, See POWERTRAIN CONTROL MODULE (PCM) . Repeat PCM Quick Test. See PCM QUICK TEST .
No If any other DTC is present, go to applicable DTC inspection.
If no DTC is present, troubleshooting complete.
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