C1102 Battery Voltage Low - Automotive Repair Guides & Equipment

COMPONENT LOCATION

GENERAL DESCRIPTION

The ABS ECU(Electronic Control Unit) checks the battery voltage and alternator output voltage to determine, as a safety issue, whether the ABS system can operate normally or not.

The normal battery voltage range is essential for controlling the ABS system as intended.

DTC DESCRIPTION

The ABS ECU monitors the battery voltage and alternator output voltage by reading the value of voltage.

When the voltage is lower than the expected normal value, this code is set.

The ABS/ESP functions are prohibited and the EBD function is allowed on LOW VOLTAGE CONDITION, the ABS/EBD/ESP functions are prohibited on UNDER VOLTAGE CONDITION.

If the voltage recovers, to within normal operating ranges, then the controller returns to normal operations as well.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible cause

DTC Strategy

Battery Voltage Monitoring

Poor connection in power supply circuit (IGN+)

Faulty HECU

Discharge of electricity

Case1
(Low voltage)

Enable
Conditions

When Vign<9.5V±0.5V is continued for 500msec during Vref >= 7Km/h.

When Vign<8.5V±0.5V is continued for 500msec during Vref < 7Km/h or ABS/ESP(ESC) control.

– If IGN voltage is recovered to normal operating voltage, the system recovers to normal state.

Fail Safe

Outside the ABS control cycle : Inhibit the ABS/ESP control, allow the EBD control , The ABS/ESP warning lamps are activated, When the voltage recovers the normal operating range, erase the error code.

Inside the ABS control cycle : Inhibit the ABS/ESP control. The ABS/ESP warning lamps are activated. Althought the voltage recovers the normal operating range, warning lamps are illuminated and the error code is always stored.

Case2
(Under voltage)

Enable
Conditions

When Vign<7.2V±0.5V is continued for 56msec.

– If IGN voltage is recovered to normal operating voltage, the system recovers to normal state.

Fail Safe

The ABS/EBD/ESP functions are inhibited.

The ABS/EBD/ESP warning lamps are activated.

SPECIFICATION

Normal Voltage Range	ENG “ON”
	10V ~ 16V

DIAGNOSTIC CIRCUIT DIAGRAM

ERMINAL AND CONNECTOR INSPECTION

1.	Many malfunctions in the electrical system are caused by poor harness(es) and terminal condition. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2.	Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

Has a problem been found?

	▶ Repair as necessary .
	▶ Go to “Alternator Output Voltage Inspection” procedure.

ALTERNATOR OUTPUT VOLTAGE INSPECTION

■ Charging System Check

1.	Ignition “ON” & Engine “ON”.

2.	Maintain ENG RPM 2,500RPM over 2 minutes.

Measure voltage between the battery terminal(+) and the battery terminal(-).

Above. 9±0.5V

Is the measured value within specifications?

	▶ Go to “Power Circuit Inspection” procedure.
	▶ Check that the tension of drive belt, ENG RPM, fuse, terminal of battery, all terminals of alternator are in good condition and Check for damaged harness and poor connection between alternator and battery. If OK repair or replace alternator .

POWER CIRCUIT INSPECTION

■ Open or Short Check

1.	Ignition “ON” & Engine “OFF”.

Measure voltage between the battery terminal(+) and power terminal of the HECU harness connector.

Approx. below 0.2V

Is the measured value within specifications?

	▶ Go to “Ground Circuit Inspection” procedure.
	▶ Check for open or blown ABS fuse referring to “Circuit Diagram”. Repair open or short in power circuit between battery and HECU harness connector

GROUND CIRCUIT INSPECTION

■ Open or Short Check

1.	Ignition “OFF” & Engine “OFF”.

2.	Disconnect HECU connector.

Measure resistance between ground terminal of the HECU harness connector and chassis ground.

Approx. below 1Ω

Is the measured value within specifications?

	▶ Substitute with a known-good HECU and check for proper operation. If problem is corrected, replace HECU
	▶ Repair open or short in ground circuit between HECU harness connector and chassis ground

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