Self-diagnostic Function

The OnStar system has a self-diagnostic function.

The self-diagnostic function is performed when the ignition switch is turned ACC (I) or ON (II).

NOTE: Most items are checked with ACC (I) except the Collision Detection Signal.

DIAGNOSIS ITEMS AND TIMING CHART

Diagnosis Items	Diagnosis Timing
Diagnosis Items	Turn the ignition switch ACC (1)	Turn the ignition switch ON (II)
OnStar control unit failure (DSP error, CPU or DSP memory error)	◦
EEPROM failure	◦
GPS receiver failure	◦
Phone module failure	◦
Collision detection signal failure		◦
Four button failure	◦
Microphone failure	◦
GPS antenna failure	◦
Phone antenna failure	◦

The OnStar control unit will store the DTCs when failures have been found in the self-diagnostic function mode. The red LED will be turned ON at the same time.

Four Button Diagnosis

The OnStar control unit will perform a four button diagnosis. When an open or short to ground failure has been found at the button input line, the OnStar control unit will store the DTC and turn the red LED ON.

Microphone Diagnosis

The OnStar control unit will perform a microphone diagnosis. When an open or short to ground failure has been found at the microphone input line, the OnStar control unit will store the DTC and turn the red LED ON.

Collision Detection Signal Diagnosis

The OnStar control unit will perform a collision detection signal diagnosis. When a failure has been found on collision detection signal circuit, the OnStar control unit will store the DTC and turn the red LED ON.

Phone Antenna Diagnosis

The OnStar control unit will perform a phone antenna diagnosis. When an open or short to ground failure has been found at the phone antenna input line, the OnStar control unit will store the DTC and turn the red LED ON.

GPS Antenna Diagnosis

The OnStar control unit will perform a GPS antenna diagnosis. When an open or short to ground has been found on the GPS antenna input line, the OnStar control unit will store the DTC and turn the red LED ON.

Example: When "door switch not received" detected

Fig 1: GPS Antenna Diagnosis Cycle Pattern - Door Switch Not Received Detected

Courtesy of AMERICAN HONDA MOTOR CO., INC.

DTC REFERENCE

First Digit	Second Digit	DTC	Detection Item
1	1	B1401	OnStar control unit internal error (CPU error) (see DTC B1401 (1-1): ONSTAR CONTROL UNIT INTERNAL ERROR (CPU ERROR) )
1	2	B1402	OnStar control unit internal error (EEPROM Error) (see DTC B1401 (1-1): ONSTAR CONTROL UNIT INTERNAL ERROR (CPU ERROR) )
1	3	B1403	GPS receiver error (see DTC B1403 (1-3): GPS RECEIVER ERROR )
1	4	B1404	Telephone module error (see DTC B1404 (1-4): TELEPHONE MODULE ERROR )
2	1	B1425	OnStar control unit lost communication with SRS unit (collision detection system) (see DTC B1408 (3-5): ONSTAR CONTROL UNIT LOST COMMUNICATION WITH GAUGE CONTROL MODULE (VSP/NE MESSAGE) )
2	3	B1428	GPS antenna circuit malfunction (see DTC B1428 (2-3): GPS ANTENNA CIRCUIT MALFUNCTION )
2	4	B1433	Cellular phone antenna circuit malfunction (see DTC B1433 (2-4): CELLULAR PHONE ANTENNA CIRCUIT MALFUNCTION )
2	5	B1426	OnStar switches circuit malfunction (see DTC B1426 (2-5): ONSTAR SWITCHES CIRCUIT MALFUNCTION )
2	6	B1427	Microphone circuit malfunction (see DTC B1427 (2-6): MICROPHONE CIRCUIT MALFUNCTION )
3	1	B1400	Communication bus line error (BUS-OFF) (see DTC B1400 (3-1): COMMUNICATION BUS LINE ERROR (BUS-OFF) )
3	2	B1405	OnStar control unit lost communication with driver's MPCS unit (DOORSW message) (see DTC B1400 (3-1): COMMUNICATION BUS LINE ERROR (BUS-OFF) )
3	3	B1406	OnStar control unit lost communication with driver's MPCS unit (DRLOCKSW message) (see DTC B1406 (3-3): ONSTAR CONTROL UNIT LOST COMMUNICATION WITH DRIVER'S MPCS UNIT (DOOR LOOK SWITCH MESSAGE) )
3	4	B1407	OnStar control unit lost communication with driver's MPCS unit (ASLOOKSW message) (see DTC B1406 (3-3): ONSTAR CONTROL UNIT LOST COMMUNICATION WITH DRIVER'S MPCS UNIT (DOOR LOOK SWITCH MESSAGE) )
3	5	B1408	OnStar control unit lost communication with gauge control module (see DTC B1408 (3-5): ONSTAR CONTROL UNIT LOST COMMUNICATION WITH GAUGE CONTROL MODULE (VSP/NE MESSAGE) )