DTC C1236 Low System Supply Voltage. Pontiac Montana 1999

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 1999 🢒 Montana 🢒 DTC 🢒 DTC C1236 Low System Supply Voltage

ABS Components
Antilock Brake System Schematics

Circuit Description

DTC C1236 monitors the voltage level available to the EBCM/EBTCM controller. If the voltage drops below 11.4 volts, full performance of the ABS system may be inhibited. During ABS operation there are several current requirements that will cause battery voltage at the EBCM/EBTCM 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 during a non-ABS event or less than 8.4 volts during an ABS event.

Action Taken When the DTC Sets

•	A malfunction DTC stores.

•	The ABS/TCS disables.

•	The amber ABS/TCS warning indicators turn on.

•	The red BRAKE warning indicator turns on if the rear piston in the ABS brake motor pack is not in the home position.

Conditions for Clearing the DTC

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

•	100 drive cycles pass with no DTC detected.

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. Refer to the Scan Tool manual or Scan Tool Diagnostics located in this section for the procedure. While performing a Voltage Load test, CKT 1639 should be measured for high resistance or an open condition if it is noted that only the ignition voltage drops below acceptable voltage levels. 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

Important: Zero the J 39200 test leads before making any resistance measurements.

Step

Action

Value(s)

Yes

Was the Diagnostic System Check performed?

Go to Step 2

Go to Diagnostic System Check - ABS

Turn the ignition switch to the RUN position, engine OFF.
Select Snapshot on the Scan Tool
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 9

Go to Step 3

Verify that the engine is running.
Select Special Functions on the Scan Tool
Use the Scan Tool to monitor the ignition voltage and the battery voltage.

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

10V

Go to Step 4

Go to Charging System Check

Turn the ignition switch to the OFF position.
Disconnect the 24-way EBCM/EBTCM connector C1.
Disconnect the 8-way EBCM/EBTCM connector C2.
Disconnect the electronic brake control relay.
Use the J 39200 and measure the resistance between the electronic brake control relay connector terminal A2 and the EBCM/EBTCM connector C2 terminal C.

Is the resistance within the specified range?

0-2ohms

Go to Step 5

Go to Step 9

Use the J 39200 and measure the voltage at the electronic brake control relay connector terminal C1.

Is the voltage within the specified range?

10.0-14.0 V

Go to Step 6

Go to Step 10

Remove and inspect the ABS/TCS IGN fuse (10A).

Is the fuse good?

Go to Step 11

Go to Step 7

Install the fuse.
Inspect the following components:

•	The harness connector for the electronic brake control relay

•	The 24-way EBCM/EBTCM connector C1

•	The 8-way EBCM/EBTCM connector C2

•	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 12

Go to Step 8

Reconnect the 24-way EBCM/EBTCM connector C1.
Reconnect the 8-way EBCM/EBTCM connector C2.
Reconnect the electronic brake control relay.
Drive the vehicle at a speed above 5 km/h (3 mph).

Does DTC C1236 set as a current DTC?

Go to Step 13

Go to Step 14

Repair the open or high resistance in CKT 1633.

Is the repair complete?

Go to Diagnostic System Check - ABS

Repair the open or high resistance in CKT 102.

Is the repair complete?

Go to Diagnostic System Check - ABS

Repair the open or high resistance in CKT 1639.

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/EBTCM.

Is the repair complete?

Go to Diagnostic System Check - ABS

The malfunction is intermittent or not present at this time.

Is a concern still present?

Go to Diagnostic Aids

Go to Diagnostic System Check - ABS