• Scan tool is essential for proper diagnosis

• 1994-1995 models: OBD1 system

• 1996-2000 models: OBD2 system

• Diagnostic codes differ between year ranges

Potential Causes

• Low or no fuel supply pump pressure

• Dirty fuel filter

• Wastegate control solenoid malfunction

Root Causes

• Low or no fuel supply pump pressure

• Retarded timing

  • Use Tech 2 scan tool for TDC offset learn procedure

  • Typically set timing to -1 to -1.5 degrees

• Low engine compression

• Cracked pistons

Potential Triggers

• Dirty air filter

• Wastegate control solenoid failure or low vacuum

• Worn injectors (excess carbon on nozzle tips)

• Low fuel supply pump pressure

• Improperly seated EGR tower gasket

• Restricted exhaust system

  • If vehicle has been "babied", catalytic converter may partially plug

  • Recommended: Perform several full-throttle accelerations to clear exhaust

Hot Start Diagnosis

• Check minimum cranking speed

• Should be at least 200 rpm when hot

Common Causes

• Worn injectors

• Overheating-related head gasket problems (typically on turbo side, cylinders #4 & #6)

• Low engine compression

• Cracked pistons

• Receives fused 12-volt power when key is on

• PCM sends signal to close fuel control solenoid

• Fuel control solenoid sends closure signal back to PMD

• Closure signal response time called C-Time

Interpretation Guidelines

• Should vary slightly during acceleration/deceleration

• Fixed C-Time can indicate bad Fuel Control Solenoid

• Erratic C-Time at stable RPM suggests bad PMD

Replacement Criteria

• Intermittent dies with no codes

• Intermittent stalling with varying C-Time

• No start condition with specific C-Time readings

  • 1.95ms (94-95 models)

  • 0.01ms (96-2000 models)

Mounting Requirements

• Must be mounted to a "heat sink"

• Use new heat transfer pad

• Torque mounting screws to 23 LB-IN

• DO NOT reuse heat transfer pad

• DO NOT over-tighten mounting screws

Operational Characteristics

• Operates during cranking and after engine oil pressure rises

• Supply pressure: 5-7 psi at idle

• Test at fuel filter drain near coolant crossover

Zero Pressure Diagnosis

1. Remove fuel supply pump relay

2. Jump connectors #30 & #80

3. Check supply pressure

4. Likely cause of zero pressure: Bad oil pressure sending switch

Diagnostic Trouble Codes

• Can trigger DTCs:

  • P0370 (17)

  • P0251 (18)

• Caused by fuel aeration

• Must "see" through fuel inside pump

• Sensitive to:

  • Air in fuel system

  • Dirty fuel

  • Straight vegetable oil (SVO)

  • Low fuel supply pressure

  • Dyed fuel

• Low resolution circuit: 8 windows

• High resolution circuit: 512 windows

• At idle, high-resolution circuit must read ~180,000 windows per minute

• For no-start condition: Disconnect encoder sensor

• Crank engine 15-20 seconds

• If engine starts, sensor is problematic

Caution: Replacement requires partial injection pump disassembly

Vacuum and Operational Characteristics

• Controlled by vacuum

• 94-2000 turbo: No spring mechanism

• Vacuum check: Should maintain 20 inches Hg

Inspection Procedure

1. Remove inlet hose from compressor inlet

2. Verify turbo spins freely

3. Check compressor wheel for housing contact

4. Some side play normal due to oil-floating bearings

Discharge Considerations

• Normal to discharge oil from compressor housing

• Assess oil input vs. output

• Plugged air filter or bad CDR valve can cause excessive oil pullout

• Multiple codes can set from single fault

• Use Tech 2 scan tool to determine:

  • First triggered code

  • Triggering conditions

P0216 (Injection Pump Timing Control)

• Check stepper motor operation

• Verify injection pump timing

• Potential crank sensor issues

P0236 (Turbo Boost Performance)

• Check wastegate control solenoid

• Verify system vacuum levels

P0251 (Injection Pump Cam Sensor)

• Check for connector issues

• Investigate fuel contamination

P0335 (Crankshaft Position Reference)

• Diagnose crank sensor and wiring

P0370 (Timing Reference High Resolution System)

• Investigate optical sensor performance

• Check for fuel system contamination

Additional DTCs

• P1125: Accelerator Pedal Position Sensor

• P1216: Fuel Solenoid Response Time (Too Short)

• P1217: Fuel Solenoid Response Time (Too Long)

• P1218: Injection Pump Calibration Resistor Error

• P1214: Injection Pump Timing Offset Error

Wear Characteristics

• Typical lifespan: ~100,000 miles

• Critical indicators of replacement need:

  • Carbon buildup

  • Poor atomization

  • Degraded spray patterns

Connector and Electrical System Check

1. Perform visual/physical connector inspection

2. Disconnect and reconnect connectors

3. Use proper terminal test tool

4. Verify:

   • Proper connector engagement

   • Terminal condition

   • Contact integrity

• Verify year-specific diagnostic procedures

• Use appropriate diagnostic equipment

• Follow manufacturer troubleshooting guidelines

• Maintain systematic diagnostic approach

• Always check for multiple potential causes of a single symptom

• Use scan tool for precise diagnostic information

• Understand year-specific system variations

• Prioritize thorough electrical system inspection