CHART - 3 - ERRATIC PERFORMANCE AND NO CODES

TM 9-2320-364-20-1

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

Section IV. TROUBLESHOOTING CHARTS (Cont.)

D. CHART - 3 - ERRATIC PERFORMANCE AND NO CODES

This is a helpful hints chart. It assumes that you have received no codes, made all the basic mechanical checks first,

could not find the problem, and suspect the DDEC III/IV system to be at fault. Based on the particular symptom here's

what to look for:

SYMPTOM

WHAT TO LOOK FOR

1. Can't get full power.

Plugged fuel filters (para 4-13 and 4-17).

Hose not connected to Turbo Boost Sensor (TBS).

Verify injector calibration(s) are correct:

Remove rocker covers (para 3-4 and 3-5). Record the

injector calibration codes found on the injector load

plate for each injector. Compare the calibration

codes with those on the DDR FUEL INJECTOR CAL

display. Update calibration codes if necessary. See

Section V for additional details. Install rocker covers

(para 3-4 and 3-5).

2. Can't get full throttle.

Incorrect Throttle Position Sensor (TPS) counts. See

Step 21-4 for details (page 2-643).

Proper gapping of Timing Reference & Synchronous

3. Runs rough, misses and/or occasionally stalls.

Reference Sensors (TRS and SRS). See

Step C 2--8 (page 2-561) on how to check this.

Check for Fuel Leaks.

Loose battery power (ckt #240 or #241), ignition

(ckt #439), or ground (ckt #150) wires.

Check power contribution from each cylinder using

cylinder cut-out feature described in Diagnostic

Data Reader (DDR) instruction manual.

Check pulse wheel: missing teeth, damaged or

loose.

Check for signs of insulation wear on injector

harnesses.

Check calibration of Throttle Position Sensor (TPS)

4. Engine idles high (after warm-up) or slow

return to idle.

using procedure in Step 21-4 (page 2-643). You

may have a TPS or pedal problem.

Check vernier control signal line (ckt #525) for

short to voltage source.