Section 4
TM 9-2320-363-20-1
TROUBLESHOOTING CHARTS
D. CHART3. POOR 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 II system to be at fault Based on the particular symptom here’s what to look for
SYMPTOM
1. Can’t get full throttle/power.
2. Runs rough, misses and/or occasionally stalls.
3. Engine idles high (after warm-up) or hangs
during shift.
4. Low road speed.
WHAT TO LOOK FOR
Miscalibrated Throttle Position Sensor (TPS). See Step
21-4 for TPS adjustment (page 3-223).
Plugged fuel filters.
Hose not connected to Turbo Boost Sensor (TBS).
Diagnostic request (ckt #451) is intermittently
shorting to ground.
Loose battery power (ckt #240 or #24 1 ) ignition
(ckt #439) or ground (ckt #1 50) wires
Check for signs of insulation wear on injector harnesses.
Check power contribution from each cylinder using the
cylinder cut-out feature described in Diagnostic Data
Reader (DDR) instruction manual.
Check calibration of the Throttle Position Sensor (TPS)
using procedure in Step 214 (page 3-223). You may
have a TPS, linkage or pedal problem.
Check PTOSA signal line (ckt #51 0) for short to
voltage source.
Determine road speed specifications from vehicle
manufacturer data. If road speed is less than specified
and all mechanical (driveline. speedometer) checks are
correct. then the EEPROM calibration is suspect. This
portion of the calibration can be reprogrammed using
Mode 37 (EEPROM CHANGES) on the Diagnostic Data
Reader (DDR). Refer to DDR Instruction Manual for
details.
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