CLEARING CODES

TM 9-2320-364-20-1

2-14. DDEC III/IV TROUBLESHOOTING (CONT).

Section III. TESTING THE DDEC III/lV SYSTEM (Cont.)

D. CLEARING CODES

This can only be done using the Diagnostic Data Reader (DDR). Refer to DDR Instruction Manual for details.

Note that removing the battery cables will not clear codes.

E. CONNECTOR CHECKOUT

All system connections are environmentally protected. These connectors protect the terminations from the harsh corrosive

engine compartment environment. This is important since most system signals are low voltage and corrosion could make

them inoperative.

Before repairing or replacing any system component (i.e., harness, sensor, ECM, etc.) as indicated by the diagnostic charts,

you should:

1. Disconnect the appropriate connector(s) associated with the suspected defective component and check for bent,

broken, or dirty terminals or mating tabs. Clean, straighten, or replace as required.

2. If a problem was found, reconnect all connectors previously disconnected. Then recheck the system to see if the

problem has been corrected.

NOTE: Don't probe the back of a connector or pierce the DDEC III wiring for purposes of taking measurement. This can cause

intermittent faults or system failures and may affect the engine warranty.

F. DIGITAL INPUT/OUTPUT FUNCTIONS

DIGITAL OUTPUTS

DDEC III/lV provides three discrete output pins on the vehicle harness which may be customized to the customer application.

These outputs provide a ground (less than 0.8 volts with respect to DDEC ground) capable of sinking up to 1 ampere of DC

current when the output is active.

The function may be selected by its "function number" found in the list below. No function should be assigned to more than one

pin (except FUNCTION #0 -- No Function).

Examples:

1. Pin J3 of the ECM's 30-pin vehicle harness connector has a transmission signal assigned to it. This function causes

the DDEC ECM to provide a signal to the ATEC ECM. This provides a signal that corresponds with the Throttle

Position Sensor. ATEC modulates shift point based on this position.

2. Pin A1 of the ECM's 30-pin vehicle harness connector has the engine brake function assigned to it. This function

causes the DDEC ECM to provide a ground to activate the engine brake relay (R7) under those conditions when the

engine brakes can be used. This function occurs under no-fuel conditions (TPS value = 0%) and when the engine

speed is greater than 1000 RPM. Relay R8 is assigned to ATEC which is included in the engine brake operation.

3. Pin K1 of the ECM's 30-pin vehicle harness connector has the engine speed function assigned to it. This function

causes the DDEC ECM to provide a digital output signal of the engine RPM to the tachometer.