DTC C1236 Low System Supply Voltage. Chevrolet Cavalier 1999

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1999 🢒 Cavalier 🢒 DTC 🢒 DTC C1236 Low System Supply Voltage

ABS Components
Antilock Brake System Schematics
Handling ESD Sensitive Parts Notice

Circuit Description

DTC C1236 monitors the voltage level available to the EBCM controller. If the voltage drops below 11.2 volts, full performance of the ABS system is not guaranteed. During ABS operation, there are several current requirements that will cause battery voltage at the EBCM to drop. As a result, voltage is monitored prior to an ABS event to indicate good charging system condition. Voltage is also monitored during an ABS event when voltage may drop significantly.

Conditions for Setting the DTC

DTC C1236 can set only if the vehicle's speed is greater than 5 km/h (3 mph).

A malfunction exists if the switched battery voltage is less than 11.4 volts without ABS being active or less than 8.4 volts during an ABS event.

Action Taken When the DTC Sets

•	A malfunction DTC stores.

•	The ABS disables.

•	The ABS warning indicator turns on.

Conditions for Clearing the DTC

•	The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.

•	100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition off.

Diagnostic Aids

The following conditions may cause an intermittent malfunction:

•	A poor connection

•	Rubbed-through wire insulation

•	A broken wire inside the insulation

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction.

Thoroughly inspect any circuitry that may be causing the intermittent complaint for the following conditions:

•	Backed out terminals

•	Improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Poor terminal-to-wiring connections

•	Physical damage to the wiring harness

While performing a Voltage Load test, CKT 439 should be measured for high resistance or an open condition if it is noted that only the ignition voltage drops below acceptable voltage levels.

Ensure the starting and charging systems are in proper working order. The battery should be fully charged and in good condition before beginning the diagnostic table. Refer to Battery and Charging System.

Test Description

This test determines if the malfunction is present.

This test checks for excessive resistance in the switched battery input circuit.

This test checks for excessive resistance in the battery feed circuit.

This test checks for an open or high resistance in the switched ignition circuit.

This test determines if the malfunction is caused by the EBCM.

Step

Action

Value(s)

Yes

Important: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.

Was the ABS Diagnostic System Check performed?

Go to Step 2

Go to Diagnostic System Check - ABS

Turn the ignition switch to the RUN position.

Do not start the engine.

Select Snapshot on the Scan Tool .
Select ABS Data.
Select Auto Trigger
Select Single DTC on the Scan Tool .
Enter C1236 on the Scan Tool .
Drive the vehicle at a speed above 5 km/h (3 mph).

Does DTC C1236 set as a current DTC?

Go to Step 3

Go to Step 17

Verify that the engine is running.
Turn the ignition switch to the RUN position.
Select Special Functions on the Scan Tool .
Use the Scan Tool in order to perform the Voltage Load test.

Are the ignition voltage and the battery voltage equal to or greater than the specified range?

10 V

Go to Step 4

Go to Step 10

Turn the ignition switch to the OFF position.
Disconnect the 24-way EBCM connector C2.
Disconnect the 8-way EBCM connector C1.
Disconnect the Electronic Brake Control Relay.
Use the J 39200 in order to measure the resistance between the Electronic Brake Control Relay connector terminal 87 and the 8-way EBCM harness connector C1 terminal C.

Is the resistance within the specified range?

0-2 ohms

Go to Step 5

Go to Step 11

Disconnect the negative battery cable.
Disconnect the positive battery cable.
Use the J 39200 in order to measure the resistance between the positive battery terminal and the Electronic Brake Control Relay connector terminal 30.

Is the resistance within the specified range?

0-2 ohms

Go to Step 6

Go to Step 12

Remove the fuse block ERLS Fuse (10A).
Use the J 39200 in order to measure the resistance between the fuse block terminal (ERLS Fuse [10A]) and the 24-way EBCM harness connector C2 terminal A9.

Is the resistance within the specified range?

0-2 ohms

Go to Step 7

Go to Step 13

Use the J 39200 in order to measure the resistance between the fuse block terminal (ERLS Fuse [10A]) and the positive battery cable.

Is the resistance within the specified range?

0-2 ohms

Go to Step 8

Go to Step 14

Inspect the following components:

•	The Electronic Brake Control Relay connector

•	The 24-way EBCM harness connector C2

•	The 8-way EBCM harness connector C1

•	The positive battery cable connections

•	The negative battery cable connections

Inspect the above components for the following conditions:

•	Terminal damage

•	Poor terminal contact

•	Terminal corrosion

•	The above conditions may cause an open circuit.

Are there signs of terminal damage, poor terminal contact, or terminal corrosion?

Go to Step 15

Go to Step 9

Reconnect the 24-way EBCM connector C2.
Reconnect the 8-way EBCM connector C1.
Reconnect the Electronic Brake Control Relay.
Reconnect the positive battery cable.
Reconnect the negative battery cable.
Drive the vehicle at a speed above 5 km/h (3 mph).

Does DTC C1236 set as a current DTC?

Go to Step 16

Go to Step 17

Repair the low voltage condition. Refer to Charging System Check in Engine Electrical.

Is the low voltage condition repaired?

Go to Diagnostic System Check - ABS

Repair the open or high resistance in CKT 1633. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Diagnostic System Check - ABS

Repair the open or high resistance in CKT 342. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Diagnostic System Check - ABS

Repair the open or high resistance in CKT 439. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Diagnostic System Check - ABS

Repair the open or high resistance in CKT 3 or CKT 1. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Diagnostic System Check - ABS

Replace all of the terminals or the connectors that exhibit signs of poor terminal contact, corrosion, or damaged terminals.

Is the repair complete?

Go to Diagnostic System Check - ABS

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Is the repair complete?

Go to Diagnostic System Check - ABS

The malfunction is intermittent or is not present at this time.

Refer to Diagnostic Aids for more information.

Is the action complete?

System OK