Speed Control Command Switch (SCCS)

1994 PCED OBDI-A

SECTION 18A: Diesel Diagnosis — 7.3L DI Engine

F: Speed Control Command Switch (SCCS)

F1 DIAGNOSTIC TROUBLE CODE (DTC)

Diagnostic Trouble Code (DTC) 831, 832, 833, 834 and 835 are set if the PCM does not detect when a key has been pressed during the key on, engine running test.

Possible causes:

Worn or damaged speed control switch
Switch shorted to battery
Open/ground short/battery short on SCCS
Open/ground short/battery short on SCGND

Perform key on, engine running self-test.
Press all speed control switches.

Is DTC 831, 832, 833, 834 or 835 present?

Yes	No
Go to F3.	GO to F2.

F2 CHECK FUSE FOR OPEN

Key off.
Check fuse PDF-30 20A in power network box for continuity.

Is fuse OK?

Yes	No
GO to F3.	REPLACE fuse. RERUN Scan Tool Diagnostic Test.

F3 CHECK CIRCUIT 151 (LB/BK) FOR OPEN

Key on, engine off.
Measure voltage at Pin 61 on the breakout box.

Is 6.6 volts present?

Yes	No
GO to F4.	GO to F6.

F4 CHECK CIRCUIT 848 (DG/O) FOR OPEN

Key off.
Disconnect brush assembly.
Measure resistance between Pin 40 on the breakout box and Circuit 848 (DG/O) at the brush assembly harness connector.

Is resistance less than 5 ohms?

Yes	No
GO to F5.	SERVICE open in Circuit 848 (DG/O). RERUN Scan Tool Diagnostic Test.

F5 CHECK BRUSH ASSEMBLY FOR OPEN

Key off.
Disconnect brush assembly from speed control switch assembly.
Measure resistance of brush assembly.

Is resistance less than 5 ohms?

Yes	No
REPLACE speed control switch. RERUN Scan Tool Diagnostic Test.	REPLACE brush assembly. RERUN Scan Tool Diagnostic Test.

F6 CHECK FOR B+ AT BRUSH ASSEMBLY

Key off.
Disconnect brush assembly.
Key on, engine off.
Measure voltage on Circuit 460 (Y/LB) at the brush assembly harness connector.

Is B+ present?

Yes	No
GO to F7.	GO to F8.

F7 CHECK BRUSH ASSEMBLY FOR OPEN

Key off.
Reconnect brush assembly.
Disconnect brush assembly from speed control switch.
Key on, engine off.
Measure voltage on Circuit 460 (Y/LB) at speed control switch harness connector.

Is B+ present?

Yes	No
REPLACE speed control switch. RERUN Scan Tool Diagnostic Test.	REPLACE brush assembly. RERUN Scan Tool Diagnostic Test.

F8 CHECK CIRCUIT 460 (Y/LB) FOR OPEN

Key off.
Disconnect horn relay.
Key on, engine off.
Measure voltage on Circuit 460 (Y/LB) at horn relay harness connector.

Is B+ present?

Yes	No
GO to F9.	REPLACE fuse. SERVICE open in Circuit 460 (Y/LB) between fuse PDF-30 20A and horn relay. RERUN Scan Tool Diagnostic Test.

F9 MEASURE HORN RELAY COIL RESISTANCE

Key off.
Disconnect horn relay.
Measure resistance of horn relay coil.

Is resistance less than 5 ohms?

Yes	No
SERVICE open in Circuit 460 (Y/LB) between horn relay and brush assembly. RERUN Scan Tool Diagnostic Test.	REPLACE horn relay.GO to F10.

F10 REPEAT KOER TEST

Perform key on, engine running test.
Press all speed control switches.

Are the same DTCs present from Step F1?

Yes	No
REPLACE speed control switch.	SERVICE intermittent connection in Circuits 151 (LB/BK) and 848 (DG/O) as necessary. RERUN Scan Tool Diagnostic Test.