DTC B1021 Driver Deployment Loop Resistance High. Isuzu S/T Isuzu

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 1998 🢒 S/T Isuzu - 2WD 🢒 DTC 🢒 DTC B1021 Driver Deployment Loop Resistance High

SRS Components
SRS Schematics
SRS Service Precautions
ESD Notice
ESD Notice

Circuit Description

When you first turn the ignition switch to the RUN position, the supplemental restraint Sensing and Diagnostic Module (SDM) performs tests to diagnose critical malfunctions within itself. Next the SDM measures IGNITION 1 and the deployment loop voltages to make sure they are within their respective normal voltage ranges. Then the SDM proceeds with the RESISTANCE MEASUREMENT test. During one portion of the RESISTANCE MEASUREMENT test, the SDM does the following:

•	Grounds the DRIVER SIDE LOW terminal 3 through an internal current sink.

•	Connects the DRIVER SIDE HIGH terminal 2 to an internal constant current source. This current produces proportional voltage drops in the deployment loop.

•	Measures the voltage difference between DRIVER SIDE HIGH and DRIVER SIDE LOW.

•	Calculates the resistance of the driver deployment loop using the measured voltage.

Conditions for Setting the DTC

•	The driver and passenger deployment loops are not open.

•	The driver and passenger deployment loops are not shorted to voltage.

•	The driver deployment loop is not shorted to ground.

•	The driver deployment loop resistance is more than 3.8 ohms. The driver deployment loop consists of the following components:

-	Supplemental restraint steering wheel module.

-	Supplemental restraint steering wheel module coil.

-	Harness wiring of CKT 347.

-	Harness wiring of CKT 348.

-	Connector terminal contact.

The RESISTANCE MEASUREMENT test checks for this malfunction. This test only occurs once each ignition cycle when IGNITION 1 is within the normal operating voltage range.

Action Taken When the DTC Sets

•	The SDM sets a Diagnostic Trouble Code.

•	The SDM turns ON the AIR BAG warning lamp.

Conditions for Clearing the DTC

The DTC will clear when one of the following conditions is met:

•	Current DTC

The resistance of the driver deployment loop is less than 3.8 ohms and the ignition switch is cycled.

•	History DTC

-	You issue a scan tool CLEAR CODES command.

-	Once 250 malfunction free ignition cycles have occurred.

When you issue a scan tool CLEAR CODES command and the malfunction is still present, the DTC will not reappear until the next ignition cycle.

Diagnostic Aids

A poor connection can cause an intermittent condition. Check the following for a poor connection:

•	The supplemental restraint steering wheel module steering column connector terminals A and B.

•	The upper supplemental restraint steering wheel module coil connector terminals A and B.

•	The SDM terminals 2 and 3.

•	The wire to terminal connections in CKT 347.

•	The wire to terminal connections in CKT 348.

The diagnostic table directs the technician to note the entry value of DRIVER RESISTANCE. Comparing the value of DRIVER RESISTANCE over multiple ignition cycles can be helpful in determining if an intermittent condition exist.

When measurements are requested in this table, use J 39200 Digital Multimeter with the correct terminal adapter from J 35616 Connector Test Adapter Kit. When an inspection for proper connection is requested, refer to Intermittents and Poor Connections . When a wire, connector or terminal repair is requested, use J-38125 Terminal Repair Kit and refer to Wiring Repair .

Test Description

The numbers below refer to the step numbers on the diagnostic table:

This test determines the deployment loop resistance measured by the supplemental restraint sensing and diagnostic module (SDM).

This test inspects for proper contact or corrosion of the yellow 2-way connector.

This test isolates the malfunction to one side of the supplemental restraint steering wheel module yellow 2-way connector.

This test determines whether the malfunction is due to the supplemental restraint steering wheel module or the module coil.

This test inspects for proper contact or corrosion of the SDM connector.

This test determines whether the malfunction is in CKT 347.

This test determines whether the malfunction is in CKT 348.

DTC B1021 -- Driver Deployment Loop Resistance High

Step	Action	Value(s)	Yes	No
1	Was the SRS Diagnostic System Check performed?	--	Go to Step 2	Go to SRS Diagnostic System Check
2	Turn the ignition switch to the OFF position. Connect the Scan Tool to the DLC. Turn the ignition switch to the RUN position. Request the SRS data list display. Read and record on the repair order the driver deployment loop resistance DRIVER RESISTANCE. Has the DRIVER RESISTANCE been read and recorded on the repair order?	--	Go to Step 3	--
3	Turn the ignition switch to the OFF position. Disconnect the supplemental restraint steering wheel yellow 2-way connector at the base of the steering column and the IP module yellow 2-way connector located behind the glove box. Inspect for proper connection at terminals A and B on the harness side of the supplemental restraint steering wheel module yellow 2-way connector at the base of the steering column. Are the terminals damaged or corroded?	--	Go to Step 4	Go to Step 6
4	Replace the yellow 2-way harness connector at the base of the steering column. Refer to Wiring Repair . Is the repair complete?	--	Go to Step 5	--
5	Inspect for proper connection at terminals A and B of the supplemental restraint steering wheel module coil side of the connector. Are the terminals damaged or corroded?	--	Go to Step 7	Go to Step 23
6	Inspect for proper connection at terminals A and B of the supplemental restraint steering wheel module coil side of the connector. Are the terminals damaged or corroded?	--	Go to Step 7	Go to Step 8
7	Replace the supplemental restraint IP module coil. Refer to Supplemental Restraint Steering Wheel Module Coil Replacement . Is the repair complete?	--	Go to Step 23	--
8	Connect the supplemental restraint steering wheel yellow 2-way connector at the base of the steering column and the IP module yellow 2-way connector located behind the glove box. Turn the ignition switch to the RUN position. Use the Scan Tool in order to request the SRS data list display. Read the driver deployment loop resistance DRIVER RESISTANCE. Is DRIVER RESISTANCE more than the specified value?	3.8 ohms	Go to Step 10	Go to Step 9
9	Turn the ignition switch to the OFF position. Replace the yellow 2-way harness connector at the base of the steering column. Refer to Wiring Repair . Is the repair complete?	--	Go to Step 23	--
10	Turn the ignition switch to the OFF position. Disconnect the supplemental restraint steering wheel yellow 2-way connector at the base of the steering column and the IP module yellow 2-way connector located behind the glove box. Connect J 38715-A SRS Driver/Passenger Load Tool to the harness connectors. Turn the ignition switch to the RUN position. Use the Scan Tool in order to request the data list display. Read the driver deployment loop resistance DRIVER RESISTANCE. Is DRIVER RESISTANCE more than the specified value?	3.8 ohms	Go to Step 14	Go to Step 11
11	Turn the ignition switch to the OFF position. Remove the supplemental restraint steering wheel module. Refer to Supplemental Restraint Steering Wheel Module Replacement . Disconnect J 38715-A from the driver 2-way connector. Connect the 2-way connector. Connect J 38715-A to the upper supplemental restraint steering wheel module coil connector on the steering column. Turn the ignition switch to the RUN position. Use the Scan Tool in order to request the SRS data list display. Read the driver deployment loop resistance DRIVER RESISTANCE. Is DRIVER RESISTANCE more than the specified value?	3.8 ohms	Go to Step 13	Go to Step 12
12	Turn the ignition switch to the OFF position. Replace the supplemental restraint steering wheel module. Refer to Supplemental Restraint Steering Wheel Module Replacement . Is the repair complete?	--	Go to Step 23	--
13	Turn the ignition switch to the OFF position. Replace the supplemental restraint steering wheel module coil. Refer to Supplemental Restraint Steering Wheel Module Coil Replacement . Is the repair complete?	--	Go to Step 23	--
14	Turn the ignition switch to the OFF position. Disconnect the SDM. Refer to Supplemental Restraint Sensing and Diagnostic Module Replacement . Disconnect J 38715-A . Inspect for proper connection at terminal 2 and terminal 3 on the harness side of the SDM connector. Is the connector damaged or corroded?	--	Go to Step 15	Go to Step 17
15	Replace the SDM harness connector. Refer to Wiring Repair . Is the repair complete?	--	Go to Step 16	--
16	Inspect for proper connection at terminal 2 and terminal 3 on the SDM. Are the terminals damaged or corroded?	--	Go to Step 18	Go to Step 23
17	Inspect for proper connection at terminal 2 and terminal 3 on the SDM. Are the terminals damaged or corroded?	--	Go to Step 18	Go to Step 19
18	Replace the SDM. Refer to Supplemental Restraint Sensing and Diagnostic Module Replacement . Is the repair complete?	--	Go to Step 23	--
19	Zero the J 39200 Digital Multimeter. Measure the resistance from the SDM harness connector terminal 2 to the supplemental restraint steering wheel module yellow 2-way harness connector terminal A. Is the resistance reading within the specified values?	0-0.5 ohms	Go to Step 21	Go to Step 20
20	Repair the high resistance condition in CKT 347. Is the repair complete?	--	Go to Step 23	--
21	Measure the resistance from the SDM harness connector terminal 3 to the supplemental restraint steering wheel module yellow 2-way harness connector terminal B. Is the resistance reading within the specified values?	0-0.5 ohms	Go to Sensing and Diagnostic Module Integrity Check	Go to Step 22
22	Repair the high resistance condition in CKT 348. Is the repair complete?	--	Go to Step 23	--
23	Reconnect all the SRS components. Ensure that all the components are properly mounted. Have all the SRS components been reconnected and properly mounted?	--	Go to Step 24	--
24	Clear all the SRS DTCs. Have all the SRS DTCs been cleared?	--	Go to SRS Diagnostic System Check	--