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Engine Controls - Basic Diagnostic Procedures Cadillac Escalade GMT400

Testing & Diagnostics ~17880 words

MODEL IDENTIFICATION

Vehicle model is identified by fifth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield. See MODEL IDENTIFICATION table.

Series (1)Model
"C"2WD Pickup, Sierra, Silverado, Suburban, Tahoe & Yukon
"G"Cutaway, Express, RV Cutaway & Savana
"K"4WD Pickup, Sierra, Silverado, Suburban, Tahoe, Yukon & AWD Escalade
"L"AWD Astro & Safari
"M"2WD Astro & Safari
"P"Forward Control (P42) & Motorhome (P32)
"S"2WD Blazer, Envoy, Jimmy, Sonoma & S10 Pickup
"T"4WD Blazer, Bravada, Envoy, Jimmy, Sonoma & S10 Pickup
"U"Montana, Silhouette & Venture
(1) Vehicle series is fifth character of VIN.
(1)Vehicle series is fifth character of VIN.

MODEL IDENTIFICATION

INTRODUCTION

The following diagnostic steps help prevent overlooking simple problems. This is also where to begin diagnosis for a no start condition.

The first step in diagnosing any driveability problem is verifying the customer's complaint by test driving vehicle under the conditions during which the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Note. Unless otherwise instructed in test procedures, perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance.

VISUAL INSPECTION

Visually inspect all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and not pinched or cut. If necessary, see appropriate VACUUM DIAGRAMS article to verify routing and connections. Inspect air induction system for possible vacuum leaks.

Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions. For compression specifications, see appropriate SERVICE & ADJUSTMENT SPECIFICATIONS article.

WARNINGBecause fuel injectors on many models are triggered by ignition switch during cranking mode, DO NOT use ignition switch during compression tests. Use a remote starter to crank engine to prevent fire hazard or contamination of engine's oiling system.

Exhaust System Backpressure

Before replacing any components, check exhaust system for restrictions. Use a vacuum gauge or a low-pressure (0-5 psi) gauge to check exhaust system.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Partially open throttle and hold steady. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for a restriction. If using a low pressure gauge, connect gauge in the following manner

  1. Check At Oxygen Sensor Remove oxygen sensor. Install backpressure tester in place of oxygen sensor. After test is completed, coat oxygen sensor threads with anti-seize compound before installation.

Diagnosis

  1. Start engine and allow it to reach normal operating temperature. Increase engine speed to 2000-2500 RPM and note gauge. If reading exceeds 1.25 psi (.09 kg/cm 2 ), exhaust system is restricted.
  2. Check exhaust system for collapsed pipe, heat distress and possible internal muffler failure. If none of these conditions exist, check for restricted catalytic converter. Replace as necessary.

NO START DIAGNOSIS

Note. For terminal and circuit identification, see appropriate wiring diagram in WIRING DIAGRAMS article.

  1. Definition No start is defined as engine cranks properly, but does not start. Engine may fire a few times.

NO START-ENGINE CRANKS OKAY (2.2L)

Note. Before performing the following tests, check battery condition, engine cranking speed and for adequate fuel in tank.

General Inspection

  1. Ensure proper starting procedure is being used. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both coil pack and spark plugs.
  2. Remove spark plugs. Check and replace as necessary. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

Ignition System

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Using scan tool, check for Diagnostic Trouble Codes (DTCs). If DTC P0601, P0602, P1621, P1626, P1631 or P1632 is present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, go to next step.
  3. Check PCM ground connection at engine block. If ground connection is faulty, go to step 5 . If ground connection is okay, go to next step.
  4. Check F/P-INJ or IGN fuses, located in underhood fuse block. If fuses are okay, go to step 6 . If any fuses are open, go to step 7 .
  5. Repair PCM ground connection. After repairs, go to step 43 .
  6. Check fuel level in tank and add if necessary. If fuel level is okay, go to step 8 . If fuel level was low and needed to be added, go to step 43 .
  7. Check for short to ground in appropriate circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. Replace faulty fuse. After repairs, go to step 43 .
  8. Install scan tool. Turn ignition on with engine off. Ensure throttle is closed. Monitor TP sensor voltage. If TP sensor voltage is less than one volt, go to next step. If TP sensor voltage is not as specified, go to DTC P0123. See appropriate SELF-DIAGNOSTICS article.
  9. Using scan tool, monitor Engine Coolant Temperature (ECT) sensor and Intake Air Temperature (IAT) sensor values. Both values should be about the same. If values are about the same, go to next step. If values are not about the same, go to DTC P0118. See appropriate SELF-DIAGNOSTICS article.
  10. Using scan tool, check MAP sensor voltage with ignition on. Voltage should be greater than 4 volts. Crank engine. If voltage was greater than 4 volts, but serial data is lost while cranking engine, go to step 13 . If MAP sensor voltage is not as specified or serial data was not lost while cranking engine, go to next step.
  11. Using scan tool, check MAP sensor voltage with ignition on. Voltage should be greater than 4 volts. Crank engine. If voltage is greater than 4 volts, then changes while cranking engine, go to next step. If MAP sensor voltage is not as specified or does not change while cranking engine, diagnose MAP sensor. See appropriate SYSTEM & COMPONENT TESTING article.
  12. Using scan tool, check Crankshaft Position (CKP) sensor activity while cranking engine. If CKP ACTIVITY COUNTER increments while cranking engine, go to step 14 . If CKP ACTIVITY COUNTER does not increment while cranking engine, go to step 24 .
  13. Repair voltage loss to PCM from ignition switch. See appropriate wiring diagram in WIRING DIAGRAMS article. After repairs, go to step 43 .
  14. Turn ignition off. Disconnect 2-pin Ignition Control Module (ICM) harness connector. Check ICM ground circuit for an open or short to power. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 43 . If ground circuit is okay, go to next step.
  15. Reconnect ICM harness connector. Install Spark Tester (J-26792) to cylinders No. 1, 2, 3 and 4 (one at a time). Connect the spark plug wire of companion cylinder to ground. Crank engine and observe spark tester. If spark is present, go to step 37 . If spark is not present, go to step 26 .
  16. Disconnect 6-pin Ignition Control Module (ICM) harness connector. Connect DVOM between CKP sensor ground circuit and CKP sensor signal circuit at ICM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Measure combined CKP sensor and wire harness resistance. If resistance is 700-1300 ohms, go to step 18 . If resistance is not as specified, go to next step.
  17. Remove CKP sensor. Ensure CKP sensor is still magnetized and terminals are not damaged. Using DVOM, measure CKP resistance. If resistance is 700-1300 ohms, go to step 20 . If resistance is not as specified, go to step 21 .
  18. Set DVOM to AC scale. Connect DVOM between CKP sensor ground circuit and CKP sensor signal circuit at ICM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Crank engine. If voltage is greater than 200 millivolts, go to next step. If voltage is not as specified, go to step 23 .
  19. Check CKP sensor signal circuit for a short to power. Repair as necessary. After repairs, go to step 43 . If CKP sensor signal circuit is okay, go to next step.
  20. Check CKP sensor signal circuit for a short to ground. Repair as necessary. After repairs, go to step 43 . If CKP sensor signal circuit is okay, go to next step.
  21. Using a test light connected to CKP 7X reference signal circuit at ICM harness connector, touch battery ground terminal, and then battery positive terminal. See appropriate wiring diagram in WIRING DIAGRAMS article. Using scan tool, monitor CKP ACTIVITY COUNTER increments. If CKP ACTIVITY COUNTER increments as test light is touched to battery positive terminal, go to step 31 . If CKP ACTIVITY COUNTER does not increment, go to step 25 .
  22. Repair open or short in CKP sensor wiring harness. After repairs, go to step 43 .
  23. Replace CKP sensor. After repairs, go to step 43 .
  24. Turn ignition off. Disconnect 2-pin Ignition Control Module (ICM) harness connector. Turn ignition on. Using a test light connected to ground, probe ignition feed circuit at ICM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 16 . If test light does not illuminate, go to step 26 .
  25. Check CKP activity (7X reference) circuit for an open or short. Repair circuit as necessary. After repairs, go to step 43 . If circuit is okay, go to step 33 .
  26. Repair faulty ignition feed circuit. After repairs, go to step 43 .
  27. Turn ignition off. Disconnect Powertrain Control Module (PCM) harness connectors. Connect spark tester to spark plug wire that did not show spark. Turn ignition on. Using a test light connected to battery positive, momentarily touch affected ignition control circuit with test light. If a spark jumps across spark tester, go to step 33 . If a spark does not jump across spark tester, go to step 34 .
  28. Using DVOM, measure resistance of spark plug wire that would not produce spark with spark tester. If resistance is less than 30,000 ohms, go to next step. If resistance is 30,000 ohms or greater, go to step 37 .
  29. Measure secondary resistance of ignition coil that did not produce a spark. If resistance is 5000-8000 ohms, go to next step. If resistance is not as specified, go to step 38 .
  30. Reconnect ICM and PCM harness connectors. Using a test light, backprobe ignition coil terminals at ICM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Crank engine and observe test light. If test light flashes, go to step 38 . If test light does not flash, go to next step.
  31. Check ICM harness connector for poor connections. Repair as necessary. After repairs, go to step 43 . If connections are okay, go to next step.
  32. Replace ICM. After repairs, go to step 43 .
  33. Check for faulty PCM connectors or connections. If connectors and connections are okay, go to step 36 . If connectors and connections are faulty, go to step 35 .
  34. Check ignition control circuit of faulty cylinder for an open or short. Repair as necessary. After repairs, go to step 43 . If circuit is okay, go to step 28 .
  35. Repair connectors or connections. After repairs, go to step 43 .
  36. Replace PCM. Perform PCM relearn procedures. After repairs, go to step 43 .
  37. Replace faulty spark plug wires. After repairs, go to step 43 .
  38. Replace faulty ignition coils. After repairs, go to step 43 .
  39. Disconnect all fuel injector harness connectors. Connect injector test light to fuel injector harness connectors No. 1, 2, 3 and 4 (one at a time). Crank engine and observe injector test light. If test light flashes at each harness connector, go to next step. If test light does not flash at each harness connector, go to step 42 .
  40. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) under BASIC FUEL SYSTEM CHECKS (GASOLINE ENGINES). Install fuel pressure gauge. Turn ignition on and note fuel pressure after 2 seconds. If fuel pressure is 41-47 psi (2.9-3.3 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to «FUEL SYSTEM ELECTRICAL CIRCUIT»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-electrical-circuit) .
  41. Check for fouled spark plugs. Replace as necessary. After repairs, go to step 43 . If spark plugs are okay, check for water in fuel system. Check for basic engine mechanical problem (low compression, etc.). Ensure spark plugs are of resistor type. Check fuel pump operation with scan tool.
  42. Repair open in fuel pump and injector ignition feed circuit. After repairs, go to next step.
  43. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and stalls, go to step 2 .
  44. Allow engine to reach normal operating temperature. Using scan tool, check for DTCs. If DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, system is okay.

Fuel System Electrical Circuit

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Ensure fuel pump relay ignition fuse is okay. If fuse is okay, go to next step. If fuse is open, go to step 20 .
  3. Install scan tool. Turn ignition on. Using scan tool, command fuel pump relay on. Fuel pump should operate for about 2 seconds. If fuel pump operates as specified, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS (GASOLINE ENGINES)»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . If fuel pump does not operate, go to next step.
  4. Remove fuel pump relay. Using a fused jumper wire, jumper fuel pump feed circuit and fuel pump relay ignition feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuel pump operates, go to next step. If fuel pump does not operate, go to step 6 .
  5. Using a test light connected to ground, probe fuel pump relay control circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Using scan tool, command fuel pump on. If test light illuminates, go to step 7 . If test light does not illuminate, go to step 8 .
  6. Using a test light connected to ground, probe ignition feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 9 . If test light does not illuminate, go to step 10 .
  7. Using a test light connected to battery positive, probe ground circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 11 . If test light does not illuminate, go to step 12 .
  8. Check for an open or short to ground in fuel pump relay control circuit. Repair as necessary. After repairs, go to step 25 . If circuit is okay, go to step 13 .
  9. Reinstall fuel pump relay. Disconnect fuel pump harness connector at fuel pump. Using a test light connected to ground, probe fuel pump feed circuit at fuel pump harness connector (body side). See appropriate wiring diagram in WIRING DIAGRAMS article. Using scan tool, command fuel pump on. If test light illuminates, go to step 14 . If test light does not illuminate, go to step 15 .
  10. Repair open in ignition feed circuit to fuel pump relay. After repairs, go to step 25 .
  11. Replace fuel pump relay. After repairs, go to step 25 .
  12. Repair open in ground circuit to fuel pump relay. After repairs, go to step 25 .
  13. Check connections and terminals to PCM. Repair as necessary. After repairs, go to step 25 . If connections and terminals are okay, go to step 16 .
  14. Using a test light connected to battery positive, probe fuel pump ground circuit at fuel pump harness connector (body side). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 17 . If test light does not illuminate, go to step 18 .
  15. Repair open in fuel pump feed circuit. After repairs, go to step 25 .
  16. Replace PCM. Perform PCM relearn procedures. After repairs, go to step 25 .
  17. Check for an open in fuel pump feed circuit and ground circuit. Repair as necessary. After repairs, go to step 25 . If circuits are okay, go to step 19 .
  18. Repair open in fuel pump ground circuit. After repairs, go to step 25 .
  19. Replace fuel pump. After repairs, go to step 25 .
  20. Turn ignition off. Disconnect fuel pump harness connector. Remove fuel pump relay. Using a test light connected to battery positive, probe fuel pump feed terminal at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 22 .
  21. Repair short to ground in fuel pump ignition feed circuit or fuel injector ignition feed circuit. After repairs, go to step 25 .
  22. Using a test light connected to battery positive, probe ignition feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 24 .
  23. Repair short to ground in fuel pump relay ignition feed circuit. After repairs, go to step 25 .
  24. Check for a short to ground in fuel pump feed circuit. Repair as necessary. After repairs, go to next step. If circuit is okay, go to step 19 .
  25. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and stalls, go to step 2 .
  26. Allow engine to reach normal operating temperature. Using scan tool, check for DTCs. If DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, system is okay.

NO START-ENGINE CRANKS OKAY (3.4L)

Note. Before performing the following tests, check battery condition, engine cranking speed and for adequate fuel in tank. Perform On-Board Diagnostic (OBD) system check following any repairs. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.

  1. Ensure proper starting procedure is being used. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both coil pack and spark plugs.
  2. Remove spark plugs. Check and replace as necessary. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Install scan tool. Using scan tool, select FAILED SINCE CODE CLEAR function. If Diagnostic Trouble Codes (DTCs) P0101, P0123, P0601/P0602, P1200, P1374, P1626 or P1629 is present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, go to next step.
  3. Turn ignition on with engine off. Using scan tool, monitor Manifold Absolute Pressure (MAP) sensor. If MAP sensor value is less than 65 kPa, go to step 27 . If MAP sensor value is 65 kPa or greater, go to next step.
  4. Turn ignition off. Disconnect Mass Airflow (MAF) sensor harness connector. Attempt to start engine. If engine starts and continues to run, go to step 27 . If engine does not start, go to next step.
  5. Turn ignition off. Reconnect MAF sensor harness connector. Install fuel pressure gauge. Turn ignition on and observe fuel pressure. If fuel pressure is 41-47 psi (2.9-3.3 kg/cm 2 ), go to step 7 . If fuel pressure is not as specified, go to next step.
  6. If fuel pressure is present, but not as specified, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS (GASOLINE ENGINES)»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . If fuel pressure is not present, go to «FUEL SYSTEM ELECTRICAL CIRCUIT»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .
  7. Turn ignition off. Disconnect 10-pin fuel injector harness connector. Using a test light connected to battery positive, probe each fuel injector driver circuit while cranking engine. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light flashes for each circuit, go to next step. If test light does not flash for each circuit, go to step 9 .
  8. Remove fuel injection fuse from underhood fuse block. Install Spark Tester (J-26792) to cylinders No. 2, 4 and 6 (one at a time). Connect spark plug wire of companion cylinder to ground. Crank engine and observe spark tester. If spark is present, go to step 19 . If spark is not present, go to step 11 .
  9. Check fuse for fuel injector feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuse is open, check for an open or shorted circuits, or shorted fuel injectors. Repair as necessary. If circuits and fuel injectors are okay, go to next step.
  10. Check for open in fuel injector feed circuit or driver circuits. Check ignition main relay feed circuits. Check for open in ignition main relay ground circuit. Check for stuck open ignition main relay or corroded contacts. Repair as necessary. If circuits or relay are okay, go to step 31 .
  11. Check fuse for Ignition Control Module (ICM) ignition feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuse is open, check for short to ground in ICM feed circuit, or short to power in IC control circuit. Repair as necessary. If fuse is okay, go to next step.
  12. Check for open in ICM feed and ground circuits. Repair as necessary. If circuits are okay, go to next step.
  13. Disconnect 2-wire 7X Crankshaft Position (CKP) sensor harness connector from ICM. Connect DVOM between CKP sensor harness connector terminals. Set DVOM to AC scale. Crank engine and observe DVOM. DVOM should indicate about 2 volts. If voltage is as specified, go to step 15 . If voltage is not as specified, go to next step.
  14. Turn ignition off. Check 7X CKP sensor circuit for open or short to power or ground. Check for poor 7X CKP sensor connection or 7X wiring harness shorted together. Repair as necessary. If circuit is okay, go to step 28 .
  15. Check for poor ICM connections. Repair as necessary. If connections are okay, go to next step.
  16. Remove and inspect ignition coil(s) that did not produce a spark. Check for cracks or carbon tracking. Replace as necessary. If coil(s) are okay, go to next step.
  17. Using DVOM, measure secondary resistance of ignition coil that did not produce a spark. Resistance should be 5000-7000 ohms. If resistance is not as specified, replace ignition coil. If resistance is as specified, go to next step.
  18. Connect a test light across affected ICM primary terminals. See appropriate wiring diagram in WIRING DIAGRAMS article. Crank engine and observe test light. If test light flashes while cranking engine, go to step 29 . If test light does not flash, go to step 30 .
  19. Check spark plug wires for cylinders No. 2, 4 and 6. Check for carbon tracking or damaged insulation. Replace as necessary. If spark plug wires are okay, go to next step.
  20. Using DVOM, measure resistance of spark plug wires for cylinders No. 2, 4 and 6. Resistance should not be greater than 7000 ohms. If resistance is not as specified, replace wires. If wires are okay, go to next step.
  21. Remove spark plugs from cylinders No. 2, 4 and 6. Check spark plug electrodes for excessive fouling. If excessive fouling is present, go to step 26 . If excessive fouling is not present, go to next step.
  22. Check spark plug wires for cylinders No. 1, 3 and 5. Check for carbon tracking or damaged insulation. Replace as necessary. If wires are okay, go to next step.
  23. Using DVOM, measure resistance of spark plug wires for cylinders No. 1, 3 and 5. Resistance should not be greater than 7000 ohms. If resistance is not as specified, replace wires. If wires are okay, go to next step.
  24. Remove spark plugs from cylinders No. 1, 3 and 5. Check spark plug electrodes for excessive fouling. If excessive fouling is present, go to step 26 . If excessive fouling is not present, go to next step.
  25. Test fuel for contamination. If fuel is contaminated, clean fuel system. If fuel is not contaminated, check PCM for poor connections or damaged connectors. Check for faulty ECT sensor, or mass airflow sensor miscalculated due to faulty TP sensor or MAP sensor. See appropriate SYSTEM & COMPONENT TESTING article.
  26. Check for engine mechanical problem. Check for bent push rods, faulty camshaft, leaking or sticky valves or rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing or leaking head gasket. Repair as necessary.
  27. Replace MAP sensor.
  28. Replace 7X CKP sensor.
  29. Replace ignition coil(s) associated with cylinder that did not produce a spark.
  30. Replace ICM.
  31. Replace PCM. Perform PCM relearn procedures.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off. Install fuel pressure gauge to fitting on fuel rail. Connect a fused jumper wire between battery positive and fuel pump test terminal in engine compartment. See appropriate wiring diagram in WIRING DIAGRAMS article. Note fuel pressure. If fuel pressure is 41-47 psi (2.9-3.3 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to step 10 .
  3. Disconnect jumper wire from fuel pump test terminal. Remove fuel pump relay. Connect a test light between battery positive voltage feed circuit and ground circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
  4. Turn ignition off. Connect a test light between ignition feed circuit (from PCM) and ground circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Observe test light while turning ignition on. If test light illuminates for about 2 seconds, go to step 8 . If test light does not illuminate as specified, go to next step.
  5. Turn ignition off. Disconnect PCM harness connectors. Using a test light connected to battery positive, probe fuel pump relay circuit at PCM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 15 . If test light does not illuminate, go to next step.
  6. Using a DVOM, check for continuity in fuel pump relay circuit between PCM and fuel pump relay. See appropriate wiring diagram in WIRING DIAGRAMS article. If circuit is open, repair as necessary. If circuit is okay, go to next step.
  7. Check fuel pump relay circuit for poor terminal connection at PCM. Repair as necessary. If terminal connection is okay, go to step 20 .
  8. Check for poor terminal connection at fuel pump relay. Repair as necessary. If connection is okay, go to step 18 .
  9. Using test light connected to ground, probe battery positive voltage feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 17 . If test light does not illuminate, go to step 16 .
  10. Remove fuel filler cap and listen for fuel pump operation. If fuel pump is operating, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS (GASOLINE ENGINES)»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . If fuel pump is not operating, leave fuel pump circuit jumpered and go to next step.
  11. Raise and support vehicle. Disconnect fuel sender harness connector at fuel tank. Connect a test light between fuel pump feed circuit and fuel pump ground circuit at fuel sender harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 19 . If test light does not illuminate, go to next step.
  12. Using test light connected to chassis ground, probe fuel pump feed circuit at fuel sender harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 14 .
  13. Locate and repair open in fuel pump ground circuit.
  14. Locate and repair open in fuel pump feed circuit.
  15. Locate and repair short to ground in fuel pump relay PCM feed circuit.
  16. Locate and repair open in ignition feed circuit to fuel pump relay.
  17. Locate and repair open in ground circuit to fuel pump relay.
  18. Replace fuel pump relay.
  19. Replace fuel pump.
  20. Replace PCM. Perform PCM relearn procedures.

NO START-ENGINE CRANKS OKAY (4.3L, 5.0L, 5.7L & 7.4L)

Note. Before performing the following tests, check battery condition, engine cranking speed and for adequate fuel in tank.

  1. Ensure proper starting procedure is being used. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both coil pack and spark plugs.
  2. Remove spark plugs. Check and replace as necessary. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

Note. VCM data is deleted when using scan tool CLEAR INFO function. Before clearing DTCs, use scan tool CAPTURE INFO function to record FREEZE FRAME and FAILURE RECORDS data.

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Attempt to start engine. If engine starts and continues to run, see appropriate TROUBLE SHOOTING - NO CODES article. If engine does not start, go to next step.
  3. For "P" series, go to next step. On all models except "P" series, install scan tool. Monitor VTD FUEL DISABLED parameter while cranking engine. If VTD FUEL DISABLED parameter is active while cranking engine, diagnose anti-theft system. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT. If VTD FUEL DISABLED parameter is not active while cranking engine, go to next step.
  4. Using scan tool, monitor Throttle Position (TP) sensor voltage with throttle closed. If TP sensor voltage is greater than 2.5 volts, go to DTC P0121. See appropriate SELF-DIAGNOSTICS article. If TP sensor voltage is 2.5 volts or less, go to next step.
  5. Using scan tool, monitor Engine Coolant Temperature (ECT) sensor. If ECT sensor value is less than -22°F (-30°C), go to DTC P0118. See appropriate SELF-DIAGNOSTICS article. If ECT sensor value is -22°F (-30°C) or greater, go to next step.
  6. Using Spark Tester (J-26792), check for spark at 2 spark plug wires while cranking engine. If spark is present at both wires, go to next step. If spark is not present at both wires, diagnose components and power, ground and signal circuits related to ignition system. See appropriate wiring diagram in WIRING DIAGRAMS article. Also see «BASIC IGNITION SYSTEM CHECKS»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Repair as necessary.
  7. Turn ignition off. Reconnect spark plug wires. Connect fuel pressure gauge. Turn ignition on with engine off. Observe fuel pressure. If fuel pressure is 55-60 psi (3.9-4.3 kg/cm 2 ), go to next step. If fuel pressure is not as specified, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS (GASOLINE ENGINES)»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .
  8. Turn ignition off. Disconnect fuel injector harness connector at intake manifold. Using a test light connected to ground, probe each fuel injector feed circuit while cranking engine. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates for each circuit, perform fuel injector coil test. See FUEL SYSTEM (GASOLINE) in appropriate SYSTEM & COMPONENT TESTING article. Also, check for any engine mechanical problems. Repair as necessary. If test light does not illuminate, diagnose fuel injector circuit. See FUEL SYSTEM (GASOLINE) in appropriate SYSTEM & COMPONENT TESTING article.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off. If fuel pump runs continuously, go to step 26 . If fuel pump does not run, go to next step.
  3. Inspect ECM B fuse (20-amp), located in underhood fuse/relay center. If fuse is okay, go to next step. If fuse is open, go to step 21 .
  4. Turn ignition on. Install scan tool. Using scan tool, command fuel pump relay on. If fuel pump operates, go to «IGNITION SYSTEM»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . If fuel pump does not operate, go to next step.
  5. Remove fuel pump relay. Using a fused jumper wire, jumper fuel pump positive feed circuit to fuel pump relay ignition feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuel pump operates, go to next step. If fuel pump does not operate, go to step 7 .
  6. Using a test light connected to ground, probe fuel pump relay control circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Using scan tool, command fuel pump on. If test light illuminates, go to step 8 . If test light does not illuminate, go to step 9 .
  7. Using a test light connected to ground, probe ignition feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 10 . If test light does not illuminate, go to step 11 .
  8. Using a test light connected to battery positive, probe ground circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 12 . If test light does not illuminate, go to step 13 .
  9. Check for an open or short to ground in fuel pump relay control circuit. Repair as necessary. After repairs, go to step 31 . If circuit is okay, go to step 14 .
  10. Reinstall fuel pump relay. Disconnect fuel pump harness connector. Using a test light connected to ground, probe fuel pump positive feed circuit at fuel pump harness connector (body harness side). See appropriate wiring diagram in WIRING DIAGRAMS article. Using scan tool, command fuel pump on. If test light illuminates, go to step 15 . If test light does not illuminate, go to step 16 .
  11. Repair open in fuel pump relay ignition feed circuit. After repairs, go to step 31 .
  12. Replace fuel pump relay. After repairs, go to step 31 .
  13. Repair open in fuel pump relay ground circuit. After repairs, go to step 31 .
  14. Check for poor connections at VCM. Repair as necessary. After repairs, go to step 31 . If connections are okay, go to step 17 .
  15. Using a test light connected to battery positive, probe ground circuit at fuel pump harness connector (body harness side). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 18 . If test light does not illuminate, go to step 19 .
  16. Repair open or short to ground in fuel pump positive feed circuit. After repairs, go to step 31 .
  17. Replace VCM. Perform VCM relearn procedures. After repairs, go to step 31 .
  18. Check fuel pump positive feed and ground circuits at fuel pump harness connector for poor connections. Repair as necessary. After repairs, go to step 31 . If connections are okay, go to step 20 .
  19. Repair open in fuel pump ground circuit. After repairs, go to step 31 .
  20. Replace fuel pump. After repairs, go to step 31 .
  21. Turn ignition off. Disconnect fuel pump harness connector. Remove fuel pump relay. Using a test light connected to battery positive, probe fuel pump positive feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 23 .
  22. Repair short to ground in fuel pump positive feed circuit. After repairs, go to step 31 .
  23. Using a test light connected to battery positive, probe ignition positive feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 25 .
  24. Repair short to ground in fuel pump relay ignition feed circuit. After repairs, go to step 31 .
  25. Check fuel pump positive feed circuit in fuel pump wiring harness (tank side) for a short to ground. Repair as necessary. After repairs, go to step 31 . If circuit is okay, go to step 20 .
  26. Remove fuel pump relay. If fuel pump continues to run, go to step 30 . If fuel pump does not run, go to next step.
  27. Turn ignition off. Using a test light connected to ground, probe fuel pump relay control circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 29 . If test light does not illuminate, go to next step.
  28. Replace fuel pump relay. After repairs, go to step 31 .
  29. Repair fuel pump relay control circuit for a short to ground. After repairs, go to step 31 .
  30. Repair fuel pump positive feed circuit for a short to power. After repairs, go to step 31 .
  31. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, go to step 4 .
  32. Allow engine to reach normal operating temperature. Using scan tool, check for DTCs. If any DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If no DTCs are present, system is okay.

NO START-ENGINE CRANKS OKAY (4.8L, 5.3L & 6.0L)

Note. Before performing the following tests, check battery condition, engine cranking speed and for adequate fuel in tank.

  1. Ensure proper starting procedure is being used. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both coil pack and spark plugs.
  2. Remove spark plugs. Check and replace as necessary. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. If Diagnostic Trouble Codes (DTCs) P0230, P0335, P0336, P0601, P0602, P0604, P1626, P1631 or any "U" codes are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If no DTCs are present, go to next step.
  3. Using scan tool, check Body Control Module (BCM) for DTCs related to Vehicle Theft Deterrent (VTD) system. If any VTD DTCs are present, diagnose DTCs. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT. If no VTD DTCs are present, go to next step.
  4. Using scan tool, monitor engine speed while cranking engine. If engine RPM is displayed, go to next step. If engine RPM is not displayed, go to step 6 .
  5. Turn ignition on with engine off. Using a test light connected to ground, probe both sides of the following fuses, located in underhood electrical center: INJR A (15-amp) INJR B (15-amp) ECM I (10-amp) If test light illuminates at both sides of all fuses, go to step 9 . If test light does not illuminate at both sides of all fuses, diagnose ignition relay. Go to «IGNITION RELAY DIAGNOSIS»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__ignition-relay-diagnosis) .
  6. Disconnect Crankshaft Position (CKP) sensor harness connector. Using DVOM, measure voltage between ground and ignition feed circuit at CKP harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If DVOM displays battery voltage, go to step 13 . If DVOM does not display battery voltage, go to next step.
  7. Disconnect Camshaft Position (CMP) sensor harness connector. Using DVOM, measure voltage between ground and ignition feed circuit at CMP harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If DVOM displays battery voltage, go to step 14 . If DVOM does not display battery voltage, go to next step.
  8. Check CKP sensor and CMP sensor ignition feed circuits for a short to ground. Repair as necessary. After repairs, go to step 16 . If circuits are okay, go to step 15 .
  9. Using scan tool, check engine coolant temperature. If displayed temperature is close to actual engine temperature, go to next step. If displayed temperature is not close to actual engine temperature, diagnose using DTC P0118. See appropriate SELF-DIAGNOSTICS article.
  10. Using scan tool, command fuel pump on. If fuel pump operates, go to next step. If fuel pump does not operate, go to «FUEL SYSTEM ELECTRICAL CIRCUIT»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .
  11. Turn ignition off. Install fuel pressure gauge. Turn ignition on. Observe fuel pressure while fuel pump is operating. If fuel pressure is 55-62 psi (3.9-4.4 kg/cm 2 ), go to next step. If fuel pressure is not as specified, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS (GASOLINE ENGINES)»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .
  12. Perform the following checks: Check air duct between Mass Airflow (MAF) sensor and throttle body for air leaks. Using scan tool, ensure throttle angle is at zero percent with throttle closed. If throttle angle is not as specified, diagnose using appropriate Throttle Position (TP) sensor DTC. See appropriate SELF-DIAGNOSTICS article. Replace MAF sensor if engine starts and continues to run with MAF sensor harness disconnected. Check for fouled spark plugs. If fouled, determine cause and repair as necessary. Check for possible engine mechanical failure causing a no start condition. Compare Manifold Absolute Pressure (MAP) sensor and barometric pressure (BARO) sensor values to that of another vehicle. Sensor values should be similar. Repair as necessary. After repairs, go to step 16 . If no problem is found, go to appropriate TROUBLE SHOOTING - NO CODES article.
  13. Replace CKP sensor. After repairs, go to step 16 .
  14. Replace CMP sensor. After repairs, go to step 16 .
  15. Replace PCM. Perform PCM relearn procedures. After repairs, go to next step.
  16. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, go to step 2 .
  17. Allow engine to reach normal operating temperature. Using scan tool, check for DTCs. If any DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If no DTCs are present, go to next step.
  18. Using scan tool, select CAPTURE INFO and REVIEW INFO function. If any DTCs are present that have not been diagnosed, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If no DTCs are present, system is okay.

Ignition Relay Diagnosis

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off. Remove IGN relay from underhood electrical center. Using a test light connected to ground, probe IGN relay battery feed circuit at IGN relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
  3. Turn ignition on with engine off. Using a test light connected to ground, probe IGN relay ignition feed circuit at IGN relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
  4. Turn ignition off. Using DVOM, measure resistance between ground and IGN relay ground circuit at IGN relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, go to step 10 .
  5. Using a fused jumper wire, jumper IGN relay battery feed circuit and IGN relay load circuit together at IGN relay connector. Using a test light connected to ground, probe both sides of the following fuses located in underhood electrical center: ENG I (10-amp) INJR A (15-amp) INJR B (15-amp) If test light illuminates at both sides of all fuses, go to next step. If test light does not illuminate at both sides of all fuses, go to step 11 .
  6. Check IGN relay for poor terminal connections. Repair as necessary. If connections are okay, go to next step.
  7. Replace IGN relay.
  8. Repair open in IGN relay battery feed circuit.
  9. Repair open in IGN relay ignition feed circuit.
  10. Repair open in IGN relay ground circuit.
  11. Repair open in IGN relay load circuit.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Check ECM B fuse (20-amp), located in underhood electrical center. If fuse is open, go to step 9 . If fuse is okay, go to next step.
  3. Remove fuel pump relay from underhood electrical center. Turn ignition on with engine off. Using a test light connected to ground, probe fuel pump relay battery feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
  4. Using a test light connected to battery positive, probe fuel pump relay ground circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13 .
  5. Install scan tool. Using a test light connected to ground, probe fuel pump relay control circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Using scan tool, command fuel pump on. If test light illuminates, go to next step. If test light does not illuminate, go to step 11 .
  6. Turn ignition on. Using a fused jumper wire, jumper fuel pump relay battery feed circuit and fuel pump load circuit together at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuel pump operates, go to step 18 . If fuel pump does not operate, leave jumper wire connected and go to next step.
  7. Disconnect fuel pump harness connector at fuel pump. Using a test light connected to ground, probe power feed circuit at fuel pump harness connector (body harness side). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, leave jumper wire connected and go to next step. If test light does not illuminate, go to step 14 .
  8. Connect test light between battery feed circuit and ground circuit at fuel pump harness connector (body harness side). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 25 . If test light does not illuminate, go to step 15 .
  9. Turn ignition off. Remove ECM B fuse (20-amp) from underhood electrical center. Disconnect fuel pump harness connector at fuel pump. Using a test light connected to battery positive, probe fuel pump relay load circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 16 . If test light does not illuminate, go to next step.
  10. Using a test light connected to battery positive, probe fuel pump relay battery feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 20 . If test light does not illuminate, go to step 21 .
  11. Turn ignition off. Disconnect PCM harness connector C2 (Red). See appropriate wiring diagram in WIRING DIAGRAMS article. Using DVOM, measure resistance of fuel pump relay control circuit between PCM and underhood electrical center. If resistance is 5 ohms or less, go to step 22 . If resistance is not as specified, go to step 17 .
  12. Repair open or short to ground in fuel pump relay battery feed circuit. Replace ECM B fuse if necessary. After repairs, go to step 26 .
  13. Repair open in fuel pump relay ground circuit. After repairs, go to step 26 .
  14. Repair open in circuit between fuel pump and fuel pump relay. After repairs, go to step 26 .
  15. Repair open in fuel pump ground circuit. After repairs, go to step 26 .
  16. Repair short to ground in fuel pump relay load circuit between fuel pump and fuel pump relay. After repairs, go to step 26 .
  17. Repair open in fuel pump relay control circuit. After repairs, go to step 26 .
  18. Check fuel pump relay for poor terminal connections. Repair as necessary. After repairs, go to step 26 . If connections are okay, go to next step.
  19. Replace fuel pump relay. After repairs, go to step 26 .
  20. Repair short to ground in fuel pump relay battery feed circuit between fuel pump relay and ECM B fuse. After repairs, go to step 26 .
  21. Turn ignition off. Reinstall fuel pump relay. Install a NEW ECM B fuse (20-amp). Reconnect fuel pump harness connector. Turn ignition on with engine off. Using scan tool, command fuel pump on. Check ECM B fuse. If fuse is open, go to step 24 . If fuse is okay, see appropriate TROUBLE SHOOTING - NO CODES article.
  22. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 26 . If connections are okay, go to next step.
  23. Replace PCM. Perform PCM relearn procedures. After repairs, go to step 26 .
  24. Check for a short to ground in fuel pump wiring harness at fuel tank. Repair as necessary. After repairs, go to step 26 . If wiring harness is okay, go to next step.
  25. Replace fuel pump. After repairs, go to step 26 .
  26. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, go to step 2 .
  27. Allow engine to reach normal operating temperature. Using scan tool, check for DTCs. If any DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If no DTCs are present, go to next step.
  28. Using scan tool, select CAPTURE INFO and REVIEW INFO function. If any DTCs are present that have not been diagnosed, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If no DTCs are present, system is okay.

NO START-ENGINE CRANKS OKAY (6.5L DIESEL)

Note. Before performing the following tests, check battery condition, engine cranking speed and for adequate fuel in tank.

Ensure proper starting procedure is being used. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. In very cold temperatures, ensure oil is proper viscosity and not contaminated. Ensure glow plug system is operating properly.

Basic System Check (Except "P" Series)

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Check battery condition. If batteries are okay, go to next step. If condition of batteries is not okay, go to step 23 .
  3. Check fuel level in tank. If fuel level is okay, go to next step. If fuel level is not okay, go to step 23 .
  4. Check quality of fuel. If fuel quality is okay, go to next step. If fuel quality is not okay, go to step 23 .
  5. Check glow plug operation. If glow plug operation is okay, go to next step. If glow plug operation is not okay, go to step 23 .
  6. Check for proper engine cranking speed. If engine cranking speed is okay, go to next step. If engine cranking speed is not okay, go to step 23 .
  7. Check for restriction in fuel return system. If restriction is not present, go to next step. If return line is restricted, go to step 23 .
  8. Check injection pump ground wire, located on top of injection pump. If ground wire is okay, go to next step. If ground wire is not okay, go to step 23 .
  9. Install scan tool. Using scan tool, check for any data. If data is displayed, go to next step. If data is not displayed, go to DLC DIAGNOSIS OR NO SCAN TOOL DATA in appropriate SELF-DIAGNOSTICS article.
  10. Using scan tool, monitor Vehicle Theft Deterrent (VTD) FUEL DISABLED parameter on ENGINE DATA 1 list. Crank engine. If scan tool displays ACTIVE while engine is cranked, diagnose VTD system. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT. If scan tool does not display ACTIVE, go to next step.
  11. Loosen injector line at injector. Crank engine and check for fuel. Repeat procedure for all injectors. If fuel flows from each fuel line, go to step 17 . If fuel does not flow from each fuel line, go to next step.
  12. Disconnect optical/fuel temperature sensor. Attempt to start engine. If engine starts, go to step 16 . If engine does not start, go to next step.
  13. Reconnect optical/fuel temperature sensor. Disconnect fuel solenoid driver at fuel injection pump. Using a DVOM, measure voltage between ground and fuel injector control circuit at harness connector while cranking engine. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is 1.2 volts or greater, go to next step. If voltage is not as specified, go to step 18 .
  14. With fuel solenoid driver still disconnected, probe solenoid ground circuit at harness connector with test light connected to battery positive. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 19 .
  15. Turn ignition on with engine off. Ensure fuel solenoid driver is still disconnected. Using a test light connected to ground, probe ignition feed circuit at fuel solenoid harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 21 .
  16. Replace fuel injection pump. After repairs, go to step 25 .
  17. Injection system is okay. See appropriate TROUBLE SHOOTING - NO CODES article.
  18. Check for open or short in fuel injector control circuit between fuel solenoid driver and PCM. Repair as necessary. After repairs, go to step 22 . If circuit is okay, go to step 20 .
  19. Check closure signal ground circuit for open between fuel solenoid driver and PCM. Repair as necessary. After repairs, go to step 22 . If circuit is okay, go to next step.
  20. Check for poor connections at fuel solenoid driver and PCM harness connectors. Repair as necessary. After repairs, go to step 22 . If connections are okay, go to step 24 .
  21. Repair open in ignition feed circuit. After repairs, go to step 25 .
  22. Repair circuit as necessary. After repairs, go to step 25 .
  23. Repair as necessary. After repairs, go to step 25 .
  24. Replace PCM. Perform PCM relearn procedures. After repairs, go to next step.
  25. Using scan tool, select DTC, CLEAR INFO function. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and stalls, go to step 2 .
  26. Allow engine to reach normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any DTCs are present, go to next step.
  27. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any other DTCs are present that have not been diagnosed, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, system is okay.

Basic System Check ("P" Series)

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Check battery condition. If batteries are okay, go to next step. If condition of batteries is not okay, go to step 23 .
  3. Check fuel level in tank. If fuel level is okay, go to next step. If fuel level is not okay, go to step 23 .
  4. Check quality of fuel. If fuel quality is okay, go to next step. If fuel quality is not okay, go to step 23 .
  5. Check glow plug operation. If glow plug operation is okay, go to next step. If glow plug operation is not okay, go to step 23 .
  6. Check for proper engine cranking speed. If engine cranking speed is okay, go to next step. If engine cranking speed is not okay, go to step 23 .
  7. Check for restriction in fuel return system. If restriction is not present, go to next step. If return line is restricted, go to step 23 .
  8. Check injection pump ground wire, located on top of injection pump. If ground wire is okay, go to next step. If ground wire is not okay, go to step 23 .
  9. Turn ignition on. If Malfunction Indicator Light (MIL) illuminates, go to next step. If MIL does not illuminate, go to appropriate MALFUNCTION INDICATOR LIGHT (MIL) in appropriate SELF-DIAGNOSTICS article.
  10. Install scan tool. Using scan tool, check for any data. If data is displayed, go to next step. If data is not displayed, go to DLC DIAGNOSIS OR NO SCAN TOOL DATA in appropriate SELF-DIAGNOSTICS article.
  11. Loosen injector line at injector. Crank engine and check for fuel. Repeat procedure for all injectors. If fuel flows from each fuel line, go to step 17 . If fuel does not flow from each fuel line, go to next step.
  12. Disconnect optical/fuel temperature sensor. Attempt to start engine. If engine starts, go to step 16 . If engine does not start, go to next step.
  13. Reconnect optical/fuel temperature sensor. Disconnect fuel solenoid driver at fuel injection pump. Using a DVOM, measure voltage between ground and fuel injector control circuit at harness connector while cranking engine. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is 1.2 volts or greater, go to next step. If voltage is not as specified, go to step 18 .
  14. With fuel solenoid driver still disconnected, probe solenoid ground circuit at harness connector with test light connected to battery positive. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 19 .
  15. Turn ignition on with engine off. Ensure fuel solenoid driver is still disconnected. Using a test light connected to ground, probe ignition feed circuit at fuel solenoid harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 21 .
  16. Replace fuel injection pump. After repairs, go to step 25 .
  17. Injection system is okay. See appropriate TROUBLE SHOOTING - NO CODES article. After repairs, go to step 25 .
  18. Check for open or short in fuel injector control circuit between fuel solenoid driver and PCM. Repair as necessary. After repairs, go to step 22 . If circuit is okay, go to step 20 .
  19. Check closure signal ground circuit for open between fuel solenoid driver and PCM. Repair as necessary. After repairs, go to step 22 . If circuit is okay, go to next step.
  20. Check for poor connections at fuel solenoid driver and PCM harness connectors. Repair as necessary. After repairs, go to step 22 . If connections are okay, go to step 24 .
  21. Repair open in ignition feed circuit. After repairs, go to step 25 .
  22. Repair circuit as necessary. After repairs, go to step 25 .
  23. Repair as necessary. After repairs, go to step 25 .
  24. Replace PCM. Perform PCM relearn procedures. After repairs, go to next step.
  25. Operate vehicle under conditions symptom was noted. If system operates properly, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. If system does not operate properly, go to step 2 .
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should operate during glow plug cycle. If fuel pump operates, go to «BASIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__basic-system-check-except-p-series) . If fuel pump does not operate, go to next step.
  3. Using a fused jumper wire, apply 12 volts to fuel pump test terminal. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuel pump operates, go to next step. If fuel pump does not operate, go to step 12 .
  4. Disconnect jumper wire from fuel pump test terminal. Turn ignition off for 10 seconds. If fuel pump operates during glow plug cycle, then stops, go to step 25 . If fuel pump does not operate as specified, go to next step.
  5. Remove fuel pump relay. Turn ignition on with engine off. Using a test light connected to ground, probe battery feed circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 14 .
  6. Connect a test light between fuel pump relay battery feed circuit and fuel pump relay ground circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 15 .
  7. Using a test light connected to ground, probe fuel pump relay control circuit at fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Turn ignition off for 20 seconds. Turn ignition on. If test light illuminates during glow plug cycle, then turns off, go to next step. If test light does not illuminate as specified, go to step 16 .
  8. Check fuel pump relay control circuit for poor connection at fuel pump relay connector. Repair as necessary. After repairs, go to step 11 . If connection is okay, go to next step.
  9. Replace fuel pump relay. After repairs, go to next step.
  10. Start engine and allow it to reach normal operating temperature. Ensure oil pressure is within normal range. Disconnect fuel pump relay. If engine continues to run, go to next step. If engine stalls, go to step 17 .
  11. Reinstall fuel pump relay. Turn ignition off. Using a test light connected to ground, probe fuel pump test connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 18 . If test light does not illuminate, go to step 25 .
  12. Disconnect fuel pump harness connector at fuel pump. Using a fused jumper wire, apply 12 volts to fuel pump test terminal. See appropriate wiring diagram in WIRING DIAGRAMS article. Using a test light connected to ground, probe fuel pump feed circuit at fuel pump harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 20 .
  13. Using test light connected to battery positive, probe fuel pump ground circuit at fuel pump harness connector (body harness side). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 19 . If test light does not illuminate, go to step 21 .
  14. Repair open in battery feed circuit to fuel pump relay connector. After repairs, go to step 25 .
  15. Repair open in fuel pump relay ground circuit. After repairs, go to step 25 .
  16. Check fuel pump relay control circuit for proper connection at PCM. See appropriate wiring diagram in WIRING DIAGRAMS article. Check for open or short to ground in fuel pump relay control circuit between fuel pump relay and PCM. If a problem is found, go to step 22 . If circuits are okay, go to step 24 .
  17. Check for proper connections at oil pressure switch harness connector. If a problem is found, go to step 22 . If connections are okay, go to next step.
  18. Replace oil pressure switch. After repairs, go to step 25 .
  19. Replace fuel pump. After repairs, go to step 25 .
  20. Repair open between fuel pump test terminal and fuel pump feed circuit at fuel pump harness connector. After repairs, go to step 25 .
  21. Repair open in fuel pump ground circuit. After repairs, go to step 25 .
  22. Repair circuit as necessary. After repairs, go to step 25 .
  23. Repair connections as necessary. After repairs, go to step 25 .
  24. Replace PCM. Perform PCM relearn procedures. After repairs, go to next step.
  25. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and stalls, go to step 2 .
  26. Allow engine to reach normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, go to next step.
  27. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any other DTCs are present that have not been diagnosed, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, system is okay.

FUEL SYSTEM PRESSURE RELIEF

CAUTIONBegin fuel system trouble shooting and diagnosis with checking fuel injection system pressure. High fuel pressure may be present in fuel lines and component parts. Relieve fuel pressure before disconnecting any fuel system components.

Note. For fuel pump circuit testing, see appropriate FUEL SYSTEM ELECTRICAL CIRCUIT in NO START DIAGNOSIS .

Fuel system is under pressure. Pressure must be relieved prior to servicing fuel system. Fuel pressure may be relieved by using one of the following method.

  1. Disconnect negative battery cable. Loosen fuel filler cap. Install Fuel Pressure Gauge (J-34730-1A) to fuel pressure connection. Wrap shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage. Place gauge bleed hose in container. Open bleed valve to relieve fuel pressure.

2.2L

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off. Turn A/C system off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Install Fuel Pressure Gauge (J-29658-D). This kit modifies fuel pressure gauge so it may be installed in fuel delivery line with quick-connect fittings. Place fuel pressure gauge bleed hose into container. Connect negative battery cable. Turn ignition on. Bleed air out of fuel pressure gauge. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm 2 ). If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step 12 .
  3. Fuel pressure may vary slightly when fuel pump stops. After fuel pump stops, fuel pressure should stabilize and remain constant. Note fuel pressure when fuel pump stops running. If fuel pressure decreases more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to step 10 . If fuel pressure does not decrease more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to next step.
  4. Relieve fuel pressure until pressure is 10 psi (0.7 kg/cm 2 ). If fuel pressure decreases more than 2 psi (0.1 kg/cm 2 ) in 10 minutes, go to step 21 . If fuel pressure does not decrease more than 2 psi (0.1 kg/cm 2 ) in 10 minutes, go to next step.
  5. If fuel pressure is suspected of decreasing during acceleration, cruise or hard cornering, go to next step. If fuel pressure is not suspected of decreasing during acceleration, cruise or hard corning, go to step 8 .
  6. Inspect in-line fuel filter and fuel feed pipe for restriction. If restriction is found, go to step 24 . If restriction is not found, go to next step.
  7. Remove fuel sending unit assembly. Inspect fuel pump strainer for restriction, proper positioning and installation on fuel sending unit assembly. Check fuel pump flex pipe for leaks and ensure fuel pump is correct for vehicle application. If a problem is found, go to step 24 . If no problem is found, go to step 20 .
  8. Start engine. Observe fuel pressure. If fuel pressure is 31-44 psi (2.2-3.1 kg/cm 2 ), system is okay. See appropriate TROUBLE SHOOTING - NO CODES article. If fuel pressure is not as specified, go to next step.
  9. Disconnect vacuum hose from fuel pressure regulator. With engine idling, apply 12-14" of vacuum to fuel pressure regulator. If fuel pressure is 31-44 psi (2.2-3.1 kg/cm 2 ) and remains constant, go to step 19 . If fuel pressure is not as specified, go to step 20 .
  10. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Place bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Using scan tool, pressurize fuel system. Wait for fuel pressure to build. Using scan tool, obtain highest fuel pressure possible. Gradually pinch off fuel feed hose. If fuel pressure remains constant, go to step 21 . If fuel pressure does not remain constant, go to next step.
  11. Gradually unpinch fuel feed hose. Using scan tool, pressurize fuel system. Wait for fuel pressure to build. Gradually pinch off fuel return hose. If fuel pressure remains constant, go to step 20 . If fuel pressure does not remain constant, go to step 22 .
  12. If fuel pressure is greater than 47 psi (3.3 kg/cm 2 ), go to next step. If fuel pressure is not greater than 47 psi (3.3 kg/cm 2 ), go to step 15 .
  13. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Disconnect fuel return pipe from fuel rail. Attach a flexible fuel hose to fuel rail return outlet passage. Place other end of flexible hose into container. Turn ignition off for about 10 seconds. Turn ignition on. Observe fuel pressure gauge with fuel pump running. Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm 2 ). If fuel pressure is within specification, go to step 23 . If fuel pressure is not within specification, go to next step.
  14. Inspect fuel rail outlet passage for restriction. If restriction is found, go to step 24 . If restriction is not found, go to step 20 .
  15. If fuel pressure is greater than zero psi, go to next step. If fuel pressure is zero psi, go to step 17 .
  16. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Place bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Using scan tool, pressurize fuel system. DO NOT allow fuel pressure to exceed 60 psi (4.2 kg/cm 2 ). Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Using scan tool, obtain highest fuel pressure possible. Gradually pinch off fuel return hose. If fuel pressure increases to greater than 47 psi (3.3 kg/cm 2 ), go to step 20 . If fuel pressure does not increase to greater 47 psi (3.3 kg/cm 2 ), go to step 7 .
  17. Check fuel pump electrical circuit. See appropriate FUEL SYSTEM ELECTRICAL CIRCUIT under «NO START DIAGNOSIS»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__no-start-diagnosis) . If a problem is found in electrical circuit, go to step 24 . If electrical circuit is okay, go to next step.
  18. Remove fuel sending unit assembly. Inspect in-line fuel filter, fuel feed pipe and fuel pump strainer for restrictions. Check fuel pump flex pipe for leaks. If a problem is found, go to step 24 . If no problem is found, go to step 21 .
  19. Locate and repair loss of vacuum to fuel pressure regulator.
  20. Replace fuel pressure regulator.
  21. Replace fuel sending unit assembly.
  22. Locate and replace leaking fuel injector(s).
  23. Locate and repair restriction in fuel return pipe.
  24. Repair problem as necessary.

3.4L

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off. Turn A/C system off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . On 3.4L, connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. On 2.2L, install Fuel Pressure Gauge (J-29658-D). This kit modifies fuel pressure gauge so it may be installed in fuel delivery line with quick-connect fittings. On all models, place fuel pressure gauge bleed hose into container. Connect negative battery cable. Turn ignition on. Bleed air out of fuel pressure gauge. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm 2 ). If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step 12 .
  3. Fuel pressure may vary slightly when fuel pump stops. After fuel pump stops, fuel pressure should stabilize and remain constant. Note fuel pressure when fuel pump stops running. If fuel pressure decreases more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to step 10 . If fuel pressure does not decrease more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to next step.
  4. Relieve fuel pressure until pressure is 10 psi (0.7 kg/cm 2 ). If fuel pressure decreases more than 2 psi (0.1 kg/cm 2 ) in 10 minutes, go to step 19 . If fuel pressure does not decrease more than 2 psi (0.1 kg/cm 2 ) in 10 minutes, go to next step.
  5. If fuel pressure is suspected of decreasing during acceleration, cruise or hard cornering, go to next step. If fuel pressure is not suspected of decreasing during acceleration, cruise or hard corning, go to step 8 .
  6. Inspect in-line fuel filter and fuel feed pipe for restriction. If restriction is found, go to step 24 . If restriction is not found, go to next step.
  7. Remove fuel sending unit assembly. Inspect fuel pump strainer for restriction, proper positioning and installation on fuel sending unit assembly. Check fuel pump flex pipe for leaks and ensure fuel pump is correct for vehicle application. If a problem is found, go to step 24 . If no problem is found, go to step 19 .
  8. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Note fuel pressure. Start engine and allow it to reach normal operating temperature. If fuel pressure is less than previously noted pressure by 3-10 psi (0.2-0.7 kg/cm 2 ), see appropriate TROUBLE SHOOTING - NO CODES article. If fuel pressure is not less than previously noted pressure by 3-10 psi (0.2-0.7 kg/cm 2 ), go to next step.
  9. Disconnect vacuum hose from fuel pressure regulator. With engine idling, apply 12-14" of vacuum to fuel pressure regulator. If fuel pressure decreases by 3-10 psi (0.2-0.7 kg/cm 2 ), go to step 20 . If fuel pressure does not decrease by 3-10 psi (0.2-0.7 kg/cm 2 ), go to step 21 .
  10. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Place bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Using scan tool, pressurize fuel system. DO NOT allow fuel pressure to exceed 65 psi (4.5 kg/cm 2 ). Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Using scan tool, obtain highest fuel pressure possible. Gradually pinch off fuel feed hose. If fuel pressure remains constant, go to step 19 . If fuel pressure does not remain constant, go to next step.
  11. Gradually unpinch fuel feed hose. Using scan tool, pressurize fuel system. Wait for fuel pressure to build. Gradually pinch off fuel return hose. If fuel pressure remains constant, go to step 21 . If fuel pressure does not remain constant, go to step 22 .
  12. If fuel pressure is greater than 47 psi (3.3 kg/cm 2 ), go to next step. If fuel pressure is not greater than 47 psi (3.3 kg/cm 2 ), go to step 15 .
  13. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Disconnect fuel return pipe from fuel rail. Attach a flexible fuel hose to fuel rail return outlet passage. Place other end of flexible hose into container. Turn ignition off for about 10 seconds. Turn ignition on. Observe fuel pressure gauge with fuel pump running. Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm 2 ). If fuel pressure is within specification, go to step 23 . If fuel pressure is not within specification, go to next step.
  14. Inspect fuel rail outlet passage for restriction. If restriction is found, go to step 24 . If restriction is not found, go to step 21 .
  15. If fuel pressure is greater than zero psi, go to next step. If fuel pressure is zero psi, go to step 17 .
  16. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Place bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Using scan tool, pressurize fuel system. DO NOT allow fuel pressure to exceed 65 psi (4.5 kg/cm 2 ). Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Using scan tool, obtain highest fuel pressure possible. Gradually pinch off fuel return hose. If fuel pressure increases to greater than 41-47 psi (2.9-3.3 kg/cm 2 ), go to step 21 . If fuel pressure does not increase to greater 41-47 psi (2.9-3.3 kg/cm 2 ), go to step 7 .
  17. Check fuel pump electrical circuit. See appropriate FUEL SYSTEM ELECTRICAL CIRCUIT under «NO START DIAGNOSIS»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__no-start-diagnosis) . If a problem is found in electrical circuit, go to step 24 . If electrical circuit is okay, go to next step.
  18. Remove fuel sending unit assembly. Inspect in-line fuel filter, fuel feed pipe and fuel pump strainer for restrictions. Check fuel pump flex pipe for leaks. If a problem is found, go to step 24 . If no problem is found, go to next step.
  19. Replace fuel sending unit assembly. After repairs, go to step 25 .
  20. Locate and repair loss of vacuum to fuel pressure regulator. After repairs, go to step 25 .
  21. Replace fuel pressure regulator. After repairs, go to step 25 .
  22. Locate and replace leaking fuel injector(s). After repairs, go to step 25 .
  23. Locate and repair restriction in fuel return pipe. After repairs, go to step 25 .
  24. Repair problem as necessary. After repairs, go to next step.
  25. Turn ignition off. Turn A/C system off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. Place fuel pressure gauge bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm 2 ). If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step 11 .
  26. Fuel pressure may vary slightly when fuel pump stops. After fuel pump stops, fuel pressure should stabilize and remain constant. Note fuel pressure when fuel pump stops running. If fuel pressure decreases more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to step 10 . If fuel pressure does not decrease more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, system is okay.

4.3L, 5.0L, 5.7L & 7.4L

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure test port. Using scan tool, command fuel pump on. Bleed air out of fuel pressure gauge into container. Monitor fuel pressure with fuel pump running. Fuel pressure should be 60-66 psi (4.2-4.6 kg/cm 2 ) on CSI system and 56-62 psi (4.0-4.4 kg/cm 2 ) on SFI system. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to step 8 .
  3. Using scan tool, command fuel pump on. Fuel pump should run for 2 seconds. Observe fuel pressure after fuel pump stops running. After fuel pump stops, fuel pressure should stabilize and remain constant at 55-60 psi (3.9-4.2 kg/cm 2 ) on CSI system and 48-52 psi (3.4-3.7 kg/cm 2 ) on SFI system. If pressure is within specification and holds, go to step 5 . If pressure is not as specified, go to next step.
  4. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Disconnect fuel filter. Drain any remaining fuel from fuel pipes into container. Install appropriate fuel line shutoff valve in place of fuel filter. Open shutoff valve. Using scan tool, command fuel pump on. Check for leaks at shutoff valve. Start engine and idle for 30 seconds. Turn ignition off for 10 seconds. Turn ignition on with engine off. Using scan tool, command fuel pump on. Wait for fuel pressure to build. Close shutoff valve. Fuel pressure should remain constant at 55-60 psi (3.9-4.2 kg/cm 2 ) on CSI system and 48-52 psi (3.4-3.7 kg/cm 2 ) on SFI system. If pressure is as specified and holds, go to step 12 . If pressure is not as specified, go to step 6 .
  5. If fuel pressure is suspected of decreasing during acceleration, cruise or hard cornering, go to step 27 . If fuel pressure is not suspected of decreasing during acceleration, cruise or hard corning, go to step 26 .
  6. Check fuel feed line between shutoff valve and fuel pipes. If fuel feed line is faulty, go to step 25 . If fuel feed line is okay, go to next step.
  7. Open shutoff valve. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Disconnect fuel return pipe union located near fuel filter. Drain remaining fuel from fuel pipes into container. Install appropriate fuel line shutoff valve in place of fuel return pipe union. Open shutoff valve. Using scan tool, command fuel pump on. Check for leaks at fuel shutoff valve fittings. Start engine and idle for 30 seconds. Turn ignition off for 10 seconds. Turn ignition on with engine off. Using scan tool, command fuel pump on. Wait for fuel pressure to build. Close shutoff valve installed on fuel return pipe. If fuel pressure remains constant, go to step 22 . If fuel pressure does not remain constant, go to step 29 .
  8. Turn ignition on with engine off. Using scan tool, command fuel pump on. Fuel pump should run for 2 seconds, and then turn off. Observe fuel pressure after fuel pump stops running. If fuel pressure is present, go to step 13 . If fuel pressure is not present, go to next step.
  9. Using scan tool, command fuel pump on. Listen for operation of fuel pump. If fuel pump operates, go to next step. If fuel pump does not operate, see appropriate FUEL SYSTEM ELECTRICAL CIRCUIT under «NO START DIAGNOSIS»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__no-start-diagnosis) .
  10. Check for restricted fuel filter, fuel pump strainer or fuel line. If a problem is found, go to next step. If no problem is found, go to step 12 .
  11. Repair or replace as necessary. After repairs, go to step 30 .
  12. Replace fuel sending unit assembly. After repairs, go to step 30 .
  13. Turn ignition on with engine off. Using scan tool, command fuel pump on. Fuel pump should run for 2 seconds. Observe fuel pressure. If fuel pressure is greater than 66 psi (4.6 kg/cm 2 ) on CSI system or greater than 62 psi (4.4 kg/cm 2 ) on SFI system, go to next step. If fuel pressure is not as specified, go to step 15 .
  14. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Disconnect engine compartment fuel return line. Attach a flexible hose to fuel return line. Place other end of hose in container. Using scan tool, command fuel pump on and observe fuel pressure within 2 seconds. Fuel pressure should be 60-66 psi (4.2-4.6 kg/cm 2 ) on CSI system and 56-62 psi (4.0-4.4 kg/cm 2 ) on SFI system. If fuel pressure is as specified, go to step 16 . If fuel pressure is not as specified, go to step 17 .
  15. Turn ignition on with engine off. Using scan tool, command fuel pump on. Fuel pump should run for 2 seconds. Observe fuel pressure. If fuel pressure is less than 60 psi (4.2 kg/cm 2 ) on CSI system or less than 56 psi (4.0 kg/cm 2 ) on SFI system, go to step 19 . If fuel pressure is not as specified, go to step 30 .
  16. Locate and repair restriction in fuel return line. After repairs, go to step 30 . If fuel return line is not restricted, go to next step.
  17. Check for restriction in engine fuel return outlet pipe at point where fuel line was disconnected. If fuel return pipe is restricted, go to next step. If fuel return pipe is not restricted, go to step 22 .
  18. Replace engine fuel pipes. After repairs, go to step 30 .
  19. Inspect in-line fuel filter and fuel line for restriction. If restriction is found, go to next step. If restriction is not found, go to step 21 .
  20. Repair or replace in-line fuel filter and fuel line as necessary. After repairs, go to step 30 .
  21. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Disconnect fuel return pipe union located near fuel filter. Drain remaining fuel from fuel pipes into container. Install appropriate fuel line shutoff valve in place of fuel return pipe union. Open shutoff valve. Using scan tool, command fuel pump on. Bleed air out of fuel pressure gauge into container. DO NOT allow fuel pressure to exceed 75 psi (4.5 kg/cm 2 ). Excess pressure may damage fuel pressure regulator. Slowly close shutoff valve installed on fuel return pipe. Fuel pressure should increase to greater than 66 psi (4.6 kg/cm 2 ) on CSI system or 62 psi (4.4 kg/cm 2 ) on SFI system. If fuel pressure increases as specified, go to next step. If fuel pressure does not increase as specified, go to step 23 .
  22. Replace fuel pressure regulator. After repairs, go to step 30 .
  23. Check for the following conditions: Low fuel pump voltage due to high resistance connections. High fuel pump voltage due to internal pump binding. Poor fuel pump ground. Partially restricted fuel pump strainer. Incorrect or faulty fuel pump. If any of the listed conditions are present, go to next step. If none of the listed conditions are present, go to step 12 .
  24. Repair or replace as necessary. After repairs, go to step 30 .
  25. Replace fuel feed line. After repairs, go to step 30 .
  26. Start engine and allow it to reach normal operating temperature. Open throttle quickly. Observe fuel pressure. Fuel pressure should increase to near 66 psi (4.6 kg/cm 2 ) on CSI system or 62 psi (4.4 kg/cm 2 ) on SFI system. If fuel pressure increases quickly, see appropriate TROUBLE SHOOTING - NO CODES article. If fuel pressure does not increase quickly, go to next step.
  27. Check for the following conditions: In-line fuel filter for restriction. Fuel feed pipe for restriction. Mispositioned or damaged fuel pump strainer. Fuel pump flex pipe for leaks. Vehicle is equipped with correct fuel pump. Fuel pump electrical wiring for high resistance. If any of the listed conditions are present, go to next step. If none of the listed conditions are present, go to step 12 .
  28. Repair or replace as necessary. After repairs, go to step 30 .
  29. Locate and replace any leaking injector(s). After repairs, go to next step. If all injectors are okay, go to FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
  30. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If additional DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, system is okay.

4.8L, 5.3L & 6.0L

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off. Turn A/C system off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Install Fuel Pressure Gauge (J-34730-1A). Place fuel pressure gauge bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be 55-62 psi (3.9-4.4 kg/cm 2 ). If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step 12 .
  3. Fuel pressure may vary slightly when fuel pump stops. After fuel pump stops, fuel pressure should stabilize and remain constant. Note fuel pressure when fuel pump stops running. If fuel pressure decreases more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to step 10 . If fuel pressure does not decrease more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to next step.
  4. Relieve fuel pressure until pressure is 10 psi (0.7 kg/cm 2 ). If fuel pressure decreases more than 2 psi (0.1 kg/cm 2 ) in 10 minutes, go to step 19 . If fuel pressure does not decrease more than 2 psi (0.1 kg/cm 2 ) in 10 minutes, go to next step.
  5. If fuel pressure is suspected of decreasing during acceleration, cruise or hard cornering, go to next step. If fuel pressure is not suspected of decreasing during acceleration, cruise or hard corning, go to step 8 .
  6. Inspect in-line fuel filter and fuel feed pipe for restriction. If restriction is found, go to step 24 . If restriction is not found, go to next step.
  7. Remove fuel sending unit assembly. Inspect fuel pump strainer for restriction, proper positioning and installation on fuel sending unit assembly. Check fuel pump flex pipe for leaks and ensure fuel pump is correct for vehicle application. If a problem is found, go to step 24 . If no problem is found, go to step 19 .
  8. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Note fuel pressure. Start engine and allow it to reach normal operating temperature. If fuel pressure is less than previously noted pressure by 3-10 psi (0.2-0.7 kg/cm 2 ), see appropriate TROUBLE SHOOTING - NO CODES article. If fuel pressure is not less than previously noted pressure by 3-10 psi (0.2-0.7 kg/cm 2 ), go to next step.
  9. Disconnect vacuum hose from fuel pressure regulator. With engine idling, apply 12-14" of vacuum to fuel pressure regulator. If fuel pressure decreases by 3-10 psi (0.2-0.7 kg/cm 2 ), go to step 20 . If fuel pressure does not decrease by 3-10 psi (0.2-0.7 kg/cm 2 ), go to step 21 .
  10. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Install appropriate fuel line shutoff valves in-line at fuel feed and fuel return lines. Open both shutoff valves. Using scan tool, pressurize fuel system. Wait for fuel pressure to build. Close shutoff valve at fuel feed line. If fuel pressure remains constant, go to step 19 . If fuel pressure does not remain constant, go to next step.
  11. Open shutoff valve at fuel feed line. Using scan tool, pressurize fuel system. Wait for fuel pressure to build. Close shutoff valve at fuel return line. If fuel pressure remains constant, go to step 21 . If fuel pressure does not remain constant, go to step 22 .
  12. If fuel pressure is greater than 62 psi (4.4 kg/cm 2 ), go to next step. If fuel pressure is not greater than 62 psi (4.4 kg/cm 2 ), go to step 15 .
  13. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Disconnect fuel return pipe from fuel rail. Attach a flexible fuel hose to fuel rail return outlet passage. Place other end of flexible hose into container. Turn ignition off for about 10 seconds. Turn ignition on. Observe fuel pressure gauge with fuel pump running. Fuel pressure should be 55-62 psi (3.9-4.4 kg/cm 2 ). If fuel pressure is within specification, go to step 23 . If fuel pressure is not within specification, go to next step.
  14. Inspect fuel rail outlet passage for restriction. If restriction is found, go to step 24 . If restriction is not found, go to step 21 .
  15. If fuel pressure is greater than zero psi, go to next step. If fuel pressure is zero psi, go to step 17 .
  16. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-relief) . Install appropriate fuel line shutoff valve in-line at fuel return line. Open shutoff valve. Using scan tool, pressurize fuel system. DO NOT allow fuel pressure to exceed 75 psi (5.3 kg/cm 2 ). Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Gradually close shutoff valve at return line. If fuel pressure increases to greater than 62 psi (4.4 kg/cm 2 ), go to step 21 . If fuel pressure does not increase to greater 62 psi (4.4 kg/cm 2 ), go to step 7 .
  17. Using scan tool, command fuel pump on. If fuel pump runs, go to next step. If fuel pump does not run, check fuel pump electrical circuit. See appropriate FUEL SYSTEM ELECTRICAL CIRCUIT under «NO START DIAGNOSIS»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__no-start-diagnosis) .
  18. Remove fuel sending unit assembly. Inspect in-line fuel filter, fuel feed pipe and fuel pump strainer for restrictions. Check fuel pump flex pipe for leaks. If a problem is found, go to step 24 . If no problem is found, go to next step.
  19. Replace fuel sending unit assembly.
  20. Locate and repair loss of vacuum to fuel pressure regulator.
  21. Replace fuel pressure regulator.
  22. Locate and replace leaking fuel injector(s).
  23. Locate and repair restriction in fuel return pipe.
  24. Repair problem as necessary.

INJECTOR CIRCUIT DIAGNOSIS

Note. This test only applies to vehicles equipped with a VCM.

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Disconnect injector harness connector at intake manifold. Turn ignition on with engine off. Using a test light connected to ground, probe injector ignition feed circuits. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates at all injector feed circuits, go to step 6 . If test light does not illuminate at all injector feed circuits, go to next step.
  3. If test light illuminates for only some of the injector circuits, go to step 5 . If test light does not illuminate for any injector circuit, go to next step.
  4. Check ECM I fuse (15-amp on 4.3L; 20-amp on all others), located in underhood fuse block. If fuse is open, go to step 10 . If fuse is okay, go to step 11 .
  5. Locate open in faulty injector feed circuit. After locating faulty circuit, go to step 12 .
  6. Install injector test light to each injector circuit, one at a time. Crank engine. If injector test light flashes on each injector, check fuel injector(s). See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If injector test light does not flash for each injector circuit, go to next step.
  7. If injector test light was on steady on any injector circuit, go to next step. If injector test light did not illuminate on any injector circuit, go to step 9 .
  8. Install injector test light to faulty injector circuit. Turn ignition off. Disconnect Red VCM harness connector. Turn ignition on with engine off. If injector test light is off, go to step 16 . If injector test light remains illuminated, go to step 13 .
  9. Check for an open in injector control circuit. If circuit is open, go to step 12 . If circuit is okay, go to step 14 .
  10. Locate short to ground in injector control circuit. After locating short, go to step 12 .
  11. Repair open or short to ground for all injector feed circuits. After repairs, go to step 17 .
  12. Repair circuit as necessary. After repairs, go to step 17 .
  13. Repair short to ground in injector control circuit. After repairs, go to step 17 .
  14. Check terminal contact at VCM harness connector. If terminal contact is faulty, go to next step. If terminal contact is okay, go to step 16 .
  15. Repair terminal contact as necessary. After repairs, go to step 17 .
  16. Replace VCM. Perform VCM reprogramming procedures. After repairs, go to next step.
  17. Using scan tool, select DTC, CLEAR INFO function. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and stalls, go to step 2 .
  18. Allow engine to reach normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any other DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If no other DTCs are present, go to next step.
  19. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If additional undiagnosed DTCs are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If additional DTCs are not present, system is okay.

FUEL PUMP FLOW TEST

  1. Remove fuse for fuel pump circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Disconnect fuel line at fuel pump outlet fitting. Install a hose at fuel pump outlet fitting and place hose in a container to collect fuel.
  2. Crank engine for 15 seconds. If fuel pump does not supply about a 1/2 pint of fuel in 15 seconds, go to «FUEL SYSTEM PRESSURE TEST»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .

FUEL SYSTEM PRESSURE TEST

Note. For fuel pump circuit testing, see appropriate FUEL SYSTEM ELECTRICAL CIRCUIT under NO START DIAGNOSIS .

  1. Turn ignition off. Install tee adapter and pressure gauge at injection pump. Start engine and measure fuel pressure.
  2. If fuel pressure is not 4 psi (.28 kg/cm 2 ), check fuel lines and fuel tank sending unit for restriction. If fuel lines and sending unit are okay, replace fuel pump.

Spark

  1. If factory tachometer is connected to coil tachometer terminal, disconnect tachometer before performing tests. When removing spark plug wire from spark plug, twist and pull on boot. DO NOT pull on wire.
  2. Using Spark Tester (J-26792), check for spark at each spark plug wire. Leave other wires connected while checking for spark. Check spark plug wire resistance on suspect wires. Resistance should be about 30,000 ohms.

Ignition Coil Power Source

CAUTIONDO NOT insert DVOM leads into ignition coil connectors. Connector terminals may be damaged. When using DVOM, ensure lead contacts front edge of terminals only.

Turn ignition on. Check ignition positive voltage circuit of ignition control module for battery voltage. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is not present, check fuse for ignition control module circuit. If fuse is not open, check for open in circuit between fuse and ignition control module.

Ignition Coil Test (2.2L, 4.3L, 5.0L, 5.7L & 7.4L)

  1. Turn ignition off. Remove engine cover. Disconnect wiring from ignition coil and distributor lead.
  2. Using DVOM, check for continuity between coil primary terminal and exterior case of coil (ground). Replace ignition coil if continuity is present.
  3. Using DVOM, measure resistance between coil primary terminals. Replace ignition coil if resistance is not 0.1 ohm.
  4. Using DVOM, measure coil secondary resistance. Replace ignition coil if resistance is not 5000-25,000 ohms.
  5. Reconnect distributor lead and wiring to ignition coil. Install engine cover.

Ignition Coil Test (4.8L, 5.3L & 6.0L)

  1. Turn ignition off. Disconnect wiring from ignition coils.
  2. Using DVOM, measure resistance between ignition coil terminal "A" and ignition coil mounting bracket. See appropriate wiring diagram in WIRING DIAGRAMS article. Replace ignition coil if resistance is not 0-10,000 ohms.
  3. Using DVOM, measure coil secondary resistance. Replace ignition coil if resistance is not 3000-7000 ohms.

Electronic Ignition System Diagnosis (Primary Ignition Check)

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. If any Diagnostic Trouble Codes (DTCs) are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, go to next step.
  3. Start engine. If a no start condition or hard-start condition is present, go to next step. If engine starts okay, go to step 5 .
  4. Turn ignition off. Disconnect Ignition Control Module (ICM) harness connector C2. Turn ignition on. Using DVOM measure voltage between ground and ignition battery voltage circuit at ICM harness connector C2. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is less than 10 volts, go to next step. If voltage is 10 volts or greater, go to «NO START-ENGINE CRANKS OKAY (3.4L)»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__no-start-engine-cranks-okay-34l) under NO START DIAGNOSIS.
  5. Drive vehicle and note driveability problems such as miss, stumble or hesitation. If driveability problem is present, go to «ELECTRONIC IGNITION SYSTEM DIAGNOSIS (SECONDARY IGNITION CHECK)»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__electronic-ignition-system-diagnosis-secondary-ignition) . If driveability problem is not present, go to next step.
  6. If any other driveability problem is present, go to appropriate TROUBLE SHOOTING - NO CODES article. If no other driveability problems are present, go to step 8 .
  7. Check ELEK IGN fuse (10-amp), located in underhood junction block. If fuse is open, repair short to ground in ignition battery voltage circuit between fuse and ICM. Replace fuse. If fuse is okay, check for open in ignition battery voltage circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Check for loose or corroded terminals and connections. Repair as necessary. After repairs, go to next step. If circuit, terminals and connections are okay, go to appropriate TROUBLE SHOOTING - NO CODES article.
  8. Operate vehicle within conditions in which problem occurred. If driveability problem is present, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. If driveability problem is not present, system is okay.

Electronic Ignition System Diagnosis (Secondary Ignition Check)

  1. Perform NO START DIAGNOSIS diagnosis. See «NO START-ENGINE CRANKS OKAY (3.4L)»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__no-start-engine-cranks-okay-34l) under NO START DIAGNOSIS. After performing no start diagnosis, go to next step.
  2. Install scan tool. Turn ignition on. If any Diagnostic Trouble Codes (DTCs) are present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, go to next step.
  3. Using scan tool, perform Fuel Injector Balance Test. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. Note cylinders with no engine speed or idle quality change. If any cylinders were noted, go to next step. If no cylinders were noted, go to step 17 .
  4. If 2 companion cylinders were noted, go to step 10 . If 2 companion cylinders were not noted, go to next step.
  5. Using DVOM, measure resistance of affected spark plug wire from end-to-end, and then from one end to ground. If spark plug wire is shorted to ground, or resistance is greater than 7000 ohms, go to step 22 . If spark plug wire is not shorted to ground, or resistance is 7000 ohms or less, go to next step.
  6. Remove affected spark plug. If spark plug looks okay, go to next step. If spark plug does not look okay, go to step 23 .
  7. Using DVOM, measure resistance of affected spark plug. If resistance is less than 10,000 ohms, go to next step. If resistance is 10,000 ohms or greater, go to step 23 .
  8. Ground companion spark plug lead of affected cylinder. Install Spark Tester (J-26792). Crank engine and note spark. If spark jumps tester gap, go to «FUEL SYSTEM PRESSURE TEST»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). If spark does not jump tester gap, go to next step.
  9. Ground affected spark plug lead. Install spark tester on companion cylinder of affected cylinder. Crank engine and note spark. If spark jumps tester gap, go to step 25 . If spark does not jump tester gap, go to step 26 .
  10. Ground one affected spark plug lead. Install spark tester on companion cylinder. Crank engine and note spark. If spark jumps tester gap, go to step 12 . If spark does not jump tester gap, go to next step.
  11. Switch affected coil with another coil and perform Fuel Injector Balance Test. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If fault follows affected coil, go to step 25 . If fault does not follow affected coil, go to step 26 .
  12. Reinstall all spark plugs and wires. Start engine and check for visible/audible arcing. If ignition system is arcing externally, go to step 27 . If ignition system is not arcing externally, go to next step.
  13. Ground other affected spark plug lead. Install spark tester on companion cylinder. Crank engine and note spark. If spark jumps tester gap, go to next step. If spark does not jump tester gap, go to step 25 .
  14. Using DVOM, measure resistance of affected spark plug wire from end-to-end, and then from one end to ground. If spark plug wire is shorted to ground, or resistance is greater than 7000 ohms, go to step 22 . If spark plug wire is not shorted to ground, or resistance is 7000 ohms or less, go to next step.
  15. Remove affected spark plugs and check for wear, damage or fouling. If both spark plugs are okay, go to next step. If spark plugs are faulty, go to step 24 .
  16. Using DVOM, measure resistance of affected spark plugs. If both spark plugs individually measure less than 10,000 ohms, go to «FUEL SYSTEM PRESSURE TEST»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). If both spark plugs individually measure 10,000 ohms or greater, go to step 24 .
  17. Install spark tester on one spark plug wire and ground companion cylinder. Note spark with engine idling. Repeat test for all spark plugs ensuring companion cylinder is grounded. If spark jumps tester gap on all cylinders, go to «FUEL SYSTEM PRESSURE TEST»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). If spark does not jump tester gap, go to next step.
  18. Switch affected coil with another coil and repeat spark tester test on all 4 cylinders of switched coils. If fault follows affected coil, go to step 25 . If fault does not follow affected coil, go to next step.
  19. Switch coils back to original location. Using DVOM, measure resistance of affected spark plug wire from end-to-end, and then from one end to ground. If either spark plug wire is shorted to ground, or resistance is greater than 7000 ohms, go to step 22 . If either spark plug wire is not shorted to ground, or resistance is 7000 ohms or less, go to next step.
  20. Remove affected spark plugs and check for wear, damage or fouling. If both spark plugs are okay, go to next step. If spark plugs are faulty, go to step 24 .
  21. Using DVOM, measure resistance of affected spark plugs. If both spark plugs individually measure less than 10,000 ohms, go to step 26 . If both spark plugs individually measure 10,000 ohms or greater, go to step 24 .
  22. Replace spark plug wire. After repairs, go to step 28 .
  23. Replace spark plug. After repairs, go to step 28 .
  24. Replace affected spark plug. After repairs, go to step 28 .
  25. Replace affected coil. After repairs, go to step 28 .
  26. Replace ICM. After repairs, go to step 28 .
  27. Repair source of arcing. After repairs, go to next step.
  28. Operate vehicle within conditions in which problem occurred. If driveability problem is present, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. If driveability problem is not present, system is okay.

IDLE SPEED & IGNITION TIMING (GASOLINE ENGINES)

Ensure idle speed and ignition timing are set to specifications. For specifications and adjustment procedures, see appropriate ON-VEHICLE ADJUSTMENTS article.

SUMMARY

If no faults were found while performing basic diagnostic procedures, or no trouble codes (or only intermittent ones) were found while performing On-Board Diagnostic (OBD) system check, and driveability problems still exist, proceed to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.

More articles — Engine Performance