DTC 21

DTC 21 Driver Deployment Loop Resistance High




Circuit Description:
When the ignition switch is turned "ON", the Sensing and Diagnostic Module (SDM) will perform tests to diagnose critical malfunctions within itself. Upon passing these tests, "ignition 1", and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges.
The SDM then proceeds with the "Resistance Measurement Test" "Driver Bag Low" terminal "4" is grounded through a current sink and the driver current source connected to "Driver Bag High" terminal "3" allows a known amount of current to flow. By monitoring the voltage difference between "Driver Bag High" and "Driver Bag Low", the SDM calculates the combined resistance of the driver air bag assembly, SRS coil assembly, harness wiring Circuits(CKTs) IB05-YELLOW and IB06-YELLOW/BLACK, and connector terminal contact.

DTC Will Set When:
The combined resistance of the driver air bag assembly, SRS Coil assembly, harness wiring CKTs IB05-YELLOW and IBO6-YELLOW/BLACK, and connector terminal contact is above a specified value. This test run once each ignition cycle during the "Resistance Measurement Test" when: No "higher priority faults" are detected during "Turn-ON" "Ignition 1" voltage is in the specified value.

Action Taken:
SDM turns "ON" the "AIR BAG" warning lamp and sets DTC 21

DTC Will Clear When:
The ignition switch is turned "OFF".

DTC 21 (Steps 1 - 3):

DTC 21 (Steps 4 - 8):

DTC Chart Test Description:
Number(s) below refer to step number(s) on the diagnostic chart:

2. This test determines whether the malfunction is in the Sensing and Diagnostic Module (SDM).
3. This test verities proper connection of the yellow 2-pin connector at the base of the steering column.
4. This test checks for proper contact and/or corrosion of the 2-pin connector terminals at the base of steering column.
5. This test isolate the malfunction to one side of the Supplemental Restraint System (SRS) coil assembly yellow 2- pin connector located at the base of the steering column.
6. This test determines whether the malfunction is due to high resistance in the wiring.
7. This test determines whether the malfunction is in the SRS coil assembly or the driver air bag assembly.

Diagnostic Aids:
An intermittent condition is likely to be caused by a poor connection at terminals "1" and "2" of the SRS coil 2-pin connector at the base of the steering column, terminal "1" and "2" of the driver air bag assembly 2-pin connector at the top of the steering column, SDM terminals "3" and "4" or a poor wire to terminal connection in Circuit IBO5-YELLOW or IB06-YELLOW/BLACK. The test for this diagnostic trouble code is only run while the "AIR BAG" warning lamp is performing the bulb check, unless Diagnostic Trouble Code (DTC) 17 or DTC 26 is detected. When a scan tool "Clear Codes" command is issued and the malfunction is still present, the DTC will not reappear until the next ignition cycle.