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Engine Controls - Basic Diagnostic Procedures GMC Yukon Denali GMT800

Testing & Diagnostics ~21851 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
"A"2WD Aztek & Rendezvous
"B"AWD Aztek & Rendezvous
"C"2WD Avalanche, Cab & Chassis, Escalade, Sierra, Silverado, Suburban, Tahoe & Yukon XL
"G"Cutaway, Express, RV Cutaway & Savana
"K"4WD Avalanche, Cab & Chassis, Escalade, Escalade EXT, Sierra, Silverado, Suburban, Tahoe, Yukon & Yukon XL
"L"AWD Astro & Safari
"M"2WD Astro & Safari
"S"2WD Blazer, Bravada, Envoy, Jimmy Canadian, Sonoma, S10 Pickup & TrailBlazer
"T"AWD/4WD Blazer, Bravada, Envoy XL, Jimmy Canadian, Sonoma, S10 Pickup & TrailBlazer
"U"Montana, Silhouette & Venture
"Z"(2) VUE
(1) Vehicle series is fifth character of VIN. (2) AWD and 2WD models.
(1)Vehicle series is fifth character of VIN.
(2)AWD and 2WD models.

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 compression gauge, vacuum gauge, or engine analyzer. See engine analyzer manual for specific instructions. For compression specifications, see SERVICE & ADJUSTMENT SPECIFICATIONS - TRUCKS article.

WARNINGFuel injectors on many models are triggered by ignition switch during cranking mode. DO NOT use ignition switch during compression tests. Use 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 vacuum gauge or low-pressure (0-5 psi) gauge to check exhaust system.

If 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 restriction. If using 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 WIRING DIAGRAMS article.

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

Preliminary Checks

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

  1. Perform OBD system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-138342-S08198199552002040800000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. After performing OBD system check, go to next step.
  2. Using scan tool, check for DTCs. If DTCs P0336, P0601, P0602, P1621, P1626, P1631, or P1632 are set, diagnose DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-138342-S05225931112002040800000) in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. If DTCs are not set, go to next step.
  3. Using scan tool, monitor CKP activity counter while cranking engine. If counter increments, go to next step. If counter does not increment, diagnose ignition system. See ELECTRONIC IGNITION SYSTEM DIAGNOSIS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  4. Turn ignition ON with engine OFF. Probe both sides of the following fuses: ECM B, ECM 1, CLSTR Fuse 11, TBC. Does the test light illuminate on both sides of all the fuses listed? If yes, go to next step. If no, diagnose fused circuit(s). See TESTING FOR SHORT TO GROUND in SYSTEM & COMPONENT TESTING - TRUCKS article.
  5. Using scan tool, command fuel pump on. If fuel pump runs, go to next step. If fuel pump does not run, diagnose fuel pump circuit. See FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  6. Turn ignition OFF. Connect fuel pressure gauge. See «BASIC FUEL SYSTEM CHECKS (GASOLINE)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Using scan tool, command fuel pump on. If fuel pressure is 41-47 psi (248-325 kPa), go to next step. If fuel pressure is not as specified, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS (GASOLINE)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .
  7. Connect Spark Tester (J-26792) to No. 1 spark plug wire. Leave other wires connected. Crank engine and check for spark. Repeat for each cylinder. If spark was present at all cylinders, go to next step. If spark was not present at all cylinders, diagnose ignition system. See ELECTRONIC IGNITION SYSTEM DIAGNOSIS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  8. Turn ignition OFF. Disconnect an injector connector. Install the Injector Test Lamp (J 34730-405) to the injector connector. Attempt to start the engine. Does the test light flash while the engine is cranking? If yes, go next step. If no, diagnose injector circuit. See FUEL INJECTOR CIRCUIT DIAGNOSIS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  9. Inspect for the following conditions; A collapsed air intake duct or restricted air filter element. Spark plugs that are gas fouled or coolant fouled. If the spark plugs are fouled, determine what caused the condition. Engine mechanical conditions, e.g. worn timing chain and gears, low compression, etc. Restricted exhaust system. The engine coolant temperature (ECT) sensor is NOT close to the actual engine temperature. See «DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE»(ref-138342-S05000045932002040800000) or «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(ref-138342-S40629955002002040800000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. Compare the Manifold Absolute Pressure (MAP) sensor and throttle position (TP) sensor parameters to another vehicle. The parameters should be close in value. See «DTC P0105: MAP/TP SENSOR CIRCUIT - INSUFFICIENT ACTIVITY»(ref-138342-S24171818082002040800000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. Did you find and correct the condition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__diagnostic-aids) .
  10. With a scan tool, clear any DTCs that are set. Attempt to start the engine. Does the engine start and continue to operate? If yes, go to next step. If engine does not start, go to step 2 .
  11. Idle the engine. Allow the engine to reach operating temperature. With a scan tool, observe the DTC information. Are any DTCs displayed? If yes, diagnose DTC. See «SELF-DIAGNOSTIC SYSTEM»(ref-138342-S41177419482002040800000) in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. If no, go to next step.
  12. With a scan tool, review the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, diagnose DTC. See «SELF-DIAGNOSTIC SYSTEM»(ref-138342-S41177419482002040800000) in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. If no, system is OK.

Diagnostic Aids

Check for proper Idle Air Control (IAC) operation. See SYSTEM & COMPONENT TESTING - TRUCKS article. Check for intermittent concerns.

NO-START - ENGINE CRANKS OKAY (2.2L VUE)

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

In order to correctly diagnose a no-start, battery voltage must be greater than 11 volts and engine must be cranking at normal cranking speed (greater than 200 RPM). Fuel level and fuel quality in fuel tank should be checked (do not rely on fuel gauge). When engine is cranked, BCM will check the password from the PassLock® sensor. If password is not received within a certain amount of time or does not match the BCM password, BCM will send a "fuel disable password" to ECM over the CAN bus. The SECURITY indicator light will flash and engine will not start. If the passwords match, BCM will send the password over the CAN bus to ECM. If ECM password does not match the BCM password, or if ECM does not receive a password from BCM, it will allow engine to start and stall within 4 seconds. The SECURITY indicator light will flash for 10 minutes if ECM receives no password, an incorrect password or a disable fuel command. If password to ECM is correct, engine will operate normally.

The password is sent continuously by the BCM to the ECM during run mode. If password becomes lost or incorrect during the drive cycle, vehicle will be allowed to start on succeeding ignition cycles without the aid of PassLock® and the SECURITY indicator light will be on steady. This mode is called fail enable mode.

  1. Ensure engine is cranking at normal cranking speed and there is sufficient fuel in fuel tank. Turn ignition on, with engine off. Using scan tool, verify that communications can be established with the BCM and ECM. If scan tool can communicate with BCM and ECM, go to next step. If scan tool does not communicate with BCM and ECM, perform Serial Data Check in Data Link Communication section in the BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  2. Are any BCM and ECM PassLock® security system or communication DTCs set (P1630, P1632 or "U" type DTCs)? If yes, diagnose affected DTC(s). See SELF-DIAGNOSTICS - 2.2L SATURN VUE article. If no, go to next step.
  3. Using scan tool, monitor IGNITION 1 voltage in the ECM General Info - Input table. If scan tool reads less than 2 volts, go to step 6 . If scan tool reads more than 2 volts, go to next step.
  4. Turn ignition off. Check IGN 1/2 fuse located in underhood fuse/relay block. Replace and retest if fuse is open. Check POWERTRAIN fuse in underhood fuse/relay block. Replace and retest if fuse is open. If affected fuse continues to open, check for short to ground in circuit. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If fuses are okay, disconnect ECM harness connector J1. Turn ignition on. Using a DVOM, check voltage between ground and ECM harness connector terminal No. 19 (Pink wire). If ignition voltage is present, go to next step. If ignition voltage is not present, circuit is open. Repair as necessary.
  5. Check ground splice for tightness. Check ECM harness connectors for terminal tightness. Repair as necessary. If ground splice and ECM harness connector terminals are okay, replace ECM.
  6. Check if any internal ECM DTCs are set. If DTCs are set, diagnose affected DTC(s). See SELF-DIAGNOSTICS - 2.2L SATURN VUE article. If no DTCs are set, go to next step.
  7. Using scan tool, monitor CKP ACTIVE COUNTER while cranking engine. If counter increments while cranking engine, go to next step. If counter does not increment while cranking engine, diagnose RPM signal loss. See Crankshaft Position (CKP) sensor diagnosis in SYSTEM & COMPONENT TESTING - TRUCKS article.
  8. Using scan tool, monitor CALC COMPRESSION OUTPUT while cranking engine. Is pattern 00000100 or 00001001 displayed on scan tool? If yes, go to next step. If no, diagnose fuel delivery system. See «FUEL SYSTEMS (GASOLINE)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  9. Turn ignition off. Check ING/INJ fuse in underhood fuse/relay block. Replace and retest as necessary. If fuse continues to open when engine is cranked, check for short to ground in circuit. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If fuse is okay, disconnect cylinder No. 4 fuel injector harness connector. Connect a Noid Light (J-34730-405) to fuel injector harness connector. Crank engine. If noid light pulses, diagnose fuel delivery system. See «BASIC FUEL SYSTEM CHECKS (GASOLINE)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . If noid light does not pulse, repair open in injector circuit.

DTCs that may cause a no-start should be diagnosed first

  1. "U" type communications DTCs.
  2. BCM or ECM PassLock® security system (DTCs P1630, P1631, P1632 or B1372).
  3. ECM internal fault DTCs.

With ignition, and engine off, ensure ECT, MAP and TP sensor readings on scan tool are normal. MAP sensor reading should be 14-15 psi (.98-1.1 kg/cm 2 ). The ECT and IAT sensor should be within 10°F (4°C) of each other with vehicle sitting overnight. A skewed sensor may cause a hard or no-start condition.

If no RPM from the CKP sensor is detected, spark and fuel will not be turned on. The signal from the CKP sensor is sent to the ECM. When engine is cranking, the scan tool CKP ACTIVE COUNTER should continuously count up to 255 then reset to zero. Check for flooded engine.

Check the following fuses in the underhood fuse/relay block. These fuses will cause a no-start, if open

  1. POWERTRAIN (10A)
  2. FUEL PUMP (10A)
  3. IGN 1/2 (30A)
  4. IGN/INJ (15A)
  5. ECM/TCM (10A)
  6. ETC (15A)
  7. BCM (10A)
  8. BCM/Cluster (10A)

NO-START - ENGINE CRANKS OKAY (3.0L VUE)

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

In order to correctly diagnose a no-start, battery voltage must be greater than 11 volts and engine must be cranking at normal cranking speed (greater than 200 RPM). Fuel level and fuel quality in fuel tank should be checked (do not rely on fuel gauge). When engine is cranked, BCM will check the password from the PassLock® sensor. If password is not received within a certain amount of time or does not match the BCM password, BCM will send a "fuel disable password" to ECM over the CAN bus. The SECURITY indicator light will flash and engine will not start. If the passwords match, BCM will send the password over the CAN bus to ECM. If ECM password does not match the BCM password, or if ECM does not receive a password from BCM, it will allow engine to start and stall within 4 seconds. The SECURITY indicator light will flash for 10 minutes if ECM receives no password, an incorrect password or a disable fuel command. If password to ECM is correct, engine will operate normally.

The password is sent continuously by the BCM to the ECM during run mode. If password becomes lost or incorrect during the drive cycle, vehicle will be allowed to start on succeeding ignition cycles without the aid of PassLock® and the SECURITY indicator light will be on steady. This mode is called fail enable mode.

  1. Ensure vehicle has adequate fuel and cranking speed is normal. Turn ignition off for 10 seconds. Turn ignition on, with engine off. Using scan tool, verify if communications can be established with the BCM and ECM. Check for DTCs. If scan tool communicates with BCM and ECM, go to next step. If scan tool does not communicate with BCM and ECM, diagnose network communications problem. See appropriate BODY CONTROL MODULES article.
  2. Check if there are any BCM/ECM PassLock® security system or communication DTCs present. If BCM DTCs are not present, go to next step. If BCM DTCs are present, see appropriate BODY CONTROL MODULES article.
  3. If ECM DTC P0601, P0602, P0603, P0604, P0606 or P0610 is set, diagnose affected DTC(s). See SELF-DIAGNOSTICS - 3.0L SATURN VUE article. If ECM DTC P0601, P0602, P0603, P0604, P0606 or P0610 is not set, go to next step.
  4. Check if fuel injector DTCs P0201-P0206 are set. If DTCs P0201-P0206 are not set, go to next step. If DTCs P0201-P0206 are set, check INJ/MAN fuse, located in underhood fuse block. Replace as necessary and retest. If fuse continues to open, check for short on injector circuits. If fuse is okay, repair open in ignition voltage circuit between fuel injectors and underhood fuse block. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
  5. Check if DTCs P0628 or P0629 is set. If any of the DTC is set, diagnose affected DTC(s). See SELF-DIAGNOSTICS - 3.0L SATURN VUE article. If no DTC is set, go to next step.
  6. Using scan tool, monitor ENGINE SPEED while cranking engine. If RPM is not detected, diagnose using DTC P0335 diagnostic procedures. See SELF-DIAGNOSTICS - 3.0L SATURN VUE article. If RPM is detected, go to next step.
  7. Turn ignition on, with engine off. Check ENG/IGN fuse in underhood fuse block. Replace as necessary and retest. If fuse continues to open, check for short to ground in ignition circuit. If fuse is okay, go to next step.
  8. Using scan tool, perform IGNITION COIL CYL 1-6 test for each individual cylinder while listening closely for spark at appropriate ignition coil. Is spark audible on each cylinder? If yes, go to next step. If no, diagnose ignition system. See «IGNITION SYSTEMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__ignition-system) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  9. Connect Fuel Pressure Gauge (SA9127E) to fuel line test port. Using scan tool, command fuel pump relay on for at least 5 seconds. If fuel pressure is 50-60 psi (3.5-4.2 kg/cm 2 ), go to next step. If fuel pressure is not 50-60 psi (3.5-4.2 kg/cm 2 ), diagnose fuel system.
  10. Turn ignition on, with engine off. Check for a normal MAF sensor voltage reading (0.8-1.2 volts) and a normal ECT sensor voltage (based on actual engine temperature). Are sensor readings within range? If yes, check for fouled spark plugs, restricted air induction, restricted exhaust, cam timing or engine mechanical failure. If no, diagnose affected sensor using appropriate DTC test procedures (P0101 - MAF or P0116 - ECT). See SELF-DIAGNOSTICS - 3.0L SATURN VUE article.

DTCs that may cause a no-start should be diagnosed first

  1. "U" type communications DTCs (U1000, U1016, U1064, U2105 or U2107).
  2. BCM or ECM PassLock® security system DTCs (P1629, P1630, P1631, P1672, B1382, B2947, B2948, B2957, B2958 or B2960).
  3. ECM internal fault DTCs.
  4. Fuel pump coil circuit DTCs (P0628 or P0629).
  5. Crankshaft Position (CKP) sensor circuit DTCs (P0335, P0337 or P0338).

If no CKP sensor signal is detected during engine crank when a valid camshaft sensor signal is received, DTC P0335 will set after a certain period of time. Fuel and spark will not be enabled.

If a MAF circuit fault occurs, the ECM will use engine speed and TP angle to calculate engine airflow. The engine will start if this condition occurs.

Turn ignition on, with engine off. Using scan tool, ensure ECT and MAF sensor voltage readings are normal. MAF sensor voltage should be 0.8-1.2 volts and ECT should be 4°F (2°C) of each other if vehicle has been sitting overnight. A skewed sensor reading may cause a hard or no-start condition.

Check for a flooded engine. To clear a flooded engine, depress accelerator pedal 100% while cranking engine. This engine is not equipped with a clear flood mode that cuts fuel off during engine crank, when flooded.

Ensure main relay is operating correctly. Listen for clicking sound when ignition is turned on. Relay is located in underhood fuse/relay block. Monitor main relay voltage on scan tool. Check the following fuses in the underhood fuse/relay block. These fuses will cause a no-start, if open

  1. ECM/TCM (10A)
  2. PWR TRAIN (10A)
  3. FUEL PUMP (10A)
  4. IGN/MAN (10A)
  5. ECM/CAM (15A)
  6. ENG/IGN (15A)
  7. IGNITION (30A)
  8. BATT (40A)

Check the following fuses in the instrument panel fuse/relay block. These fuses will cause a no-start, if open

  1. BCM/IGN (10A)
  2. BCM/CLUSTER (10A)

Before performing the following tests, check battery condition, engine cranking speed and for adequate fuel in tank. Perform OBD system check following any repairs. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE or SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article.

Test Description

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 3 This step determines if ignition relay is providing listed fuses with voltage.
  2. 4 If all Cylinder Injector Circuit Status parameters display Fault, this indicates a condition with injector supply voltage circuit.
  3. 5 This step determines if fuel pump is operating electrically.
  4. 8 This step determines if Camshaft Position (CMP) sensor is functioning properly.
  1. Perform OBD system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in «SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE»(ref-140805) or «SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS»(ref-140049) article. After performing OBD system check, go to next step.
  2. Using scan tool, check for DTCs. If DTCs P0101, P0123, P0230, P0336, P0341, P0601, P0602, P1626, P1630, or P1631 are set, diagnose DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in «SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE»(ref-140805) or «SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS»(ref-140049) article. If DTCs are not set, go to next step.
  3. Turn ignition ON, with engine OFF. Probe both sides of the following fuses: IGN 1-U/H, ELEC IGN, IGN MAIN 1 and 2, and Fuel INJ. Does the test light illuminate on both sides of all the fuses listed? If yes, go to next step. If no, diagnose ignition relay or individual fuse.
  4. Monitor the Cylinder 1-6 Injector Circuit Status parameters with a scan tool. Crank the engine. Do all of the Cylinder Injector Circuit Status parameters display OK? If yes, go to next step. If no, diagnose fuel injector circuit. See FUEL INJECTOR CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  5. Using scan tool, command fuel pump ON. If fuel pump runs, go to next step. If fuel pump does not run, diagnose fuel pump circuit. See FUEL PUMP ELECTRICAL CIRCUIT under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  6. Connect Spark Tester (J-26792) to No. 1 spark plug wire. Leave other wires connected. Crank engine and check for spark. Repeat for each cylinder. If spark was present at all cylinders, go to next step. If spark was not present at all cylinders, diagnose ignition system. See ELECTRONIC IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  7. Turn ignition OFF. Connect all disconnected components. Install Fuel Pressure Gauge (J 34730-1A). Turn ignition ON, with engine OFF. Command the fuel pump ON with a scan tool. Is the fuel pressure 52-59 psi (358-405 kPa) when the fuel pump is operating? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  8. Disconnect fuel injector harness multi-way connector. Jumper 3 Camshaft Position (CMP) sensor circuits between fuel injector harness multi-way connectors. Probe fuel injector control circuits, PCM side of connector, with test light connected to positive battery terminal. Crank engine. Does test light blink while cranking engine? If yes, go to next step. If no, diagnose fuel injector driver circuits. See DTC P0341: CAMSHAFT POSITION SENSOR CIRCUIT PERFORMANCE under DIAGNOSTIC TESTS in «SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE»(ref-140805) or «SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS»(ref-140049) article.
  9. Inspect for the following conditions; A collapsed air intake duct or restricted air filter element. Spark plugs that are gas fouled or coolant fouled. If the spark plugs are fouled, determine what caused the condition. Engine mechanical conditions, e.g. worn timing chain and gears, low compression, etc. Restricted exhaust system. The engine coolant temperature (ECT) sensor is NOT close to the actual engine temperature. For Montana, Silhouette and Venture, diagnose DTC P0117 or DTC P0118 under DIAGNOSTIC TESTS in «SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE»(ref-140805) article. For Aztec and Rendezvous, diagnose DTC P0128 under DIAGNOSTIC TESTS in «SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS»(ref-140049) article. Compare the Manifold Absolute Pressure (MAP) sensor and throttle position (TP) sensor parameters to another vehicle. The parameters should be close in value. For Montana, Silhouette and Venture, diagnose DTC P0105 under DIAGNOSTIC TESTS in «SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE»(ref-140805) article. For Aztec and Rendezvous, diagnose DTC P0121 under DIAGNOSTIC TESTS in «SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS»(ref-140049) article. Did you find and correct the condition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__diagnostic-aids) .
  10. With a scan tool, clear any DTCs that are set. Attempt to start the engine. Does the engine start and continue to operate? If yes, go to next step. If engine does not start, go to step 2 .
  11. Allow the engine to reach operating temperature. Observe the DTC information with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, diagnose DTC. See «SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE»(ref-140805) or «SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS»(ref-140049) article. If no, system is OK.

Inspect for the following conditions

  1. Mass Air Flow (MAF) is compared to a calculated mass air flow based upon the manifold absolute pressure (MAP), the throttle position (TP), and the engine RPM readings. A skewed or unresponsive MAP sensor at KEY ON will cause the predicted air flow value to be inaccurate. Compare the MAP and the TP sensor value to that of a known good vehicle.
  2. Faulty engine coolant temperature (ECT) sensor. Using a scan tool, compare engine coolant temperature with intake air temperature (IAT) on a completely cool engine. The engine coolant temperature should be within 5°F (3°C) of the intake air temperature. If not, diagnose DTC P0128. See «SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE»(ref-140805) or «SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS»(ref-140049) article.
  3. For intermittent condition testing, see «INTERMITTENTS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__intermittents) in TROUBLESHOOTING - NO CODES - TRUCKS article.

Description

No-Start - Engine Cranks Okay diagnostic procedure is an organized approach to identifying a condition that causes an engine not to start. No-Start - Engine Cranks Okay diagnostic procedure directs service technician to appropriate system diagnosis. No-Start - Engine Cranks Okay diagnostic procedure assumes the following

  1. Battery is completely charged.
  2. Cranking speed is acceptable.
  3. There is adequate fuel in fuel tank.

The numbers below refer to step numbers in diagnostic procedure.

  1. 8 Crankshaft Position (CKP) sensor can fail in such a way that will cause engine to crank but will not run. Engine will be able to run by using CMP sensor when CKP sensor is disconnected.
  1. Perform OBD system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-132531-S16910731432002012100000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article. After performing OBD system check, go to next step.
  2. Turn ON the ignition, with the engine OFF. With scan tool, observe DTC information. Does scan tool display DTC P0107, P0601, P0602, P0604, P0606, P0607, P1220, P1221, P1271, P1514, P1621, P1631, P1635, P1639, P1680, P1681, or P1683? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-132531-S07878208602002012100000) in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article. If no, go to next step.
  3. Monitor Ignition 1 Signal Voltage parameter with scan tool. Does Ignition 1 Signal Voltage parameter read battery voltage? If yes, go to next step. If no, go to step 10 .
  4. Command fuel pump ON with scan tool. Does fuel pump turn ON? If yes, go to next step. If no, go to «FUEL PUMP RELAY (ALL EXCEPT 2.2L & 3.0L VUE, 3.4L, 5.0L & 5.7L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-pump-relay-all-except-22l) under FUEL SYSTEM (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  5. Turn OFF the ignition. Remove an ignition coil. Install (J 26792) Spark Tester to coil boot. Attempt to start engine. Does spark tester spark? If yes, go to next step. If no, go to «ELECTRONIC IGNITION SYSTEM DIAGNOSIS (4.2L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__electronic-ignition-system-diagnosis-42l) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  6. Turn OFF the ignition. Disconnect fuel injector harness multi-way connector. Probe a fuel injector control circuit, PCM side, with test light connected to battery voltage. Crank engine. Does test light flash when cranking engine? If yes, go to next step. If no, go to «FUEL INJECTOR CIRCUIT DIAGNOSIS (4.2L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-injector-circuit-diagnosis-42l) under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  7. Turn OFF the ignition. Install (J 34730-1A) Fuel Pressure Gauge. Turn ON the ignition, with the engine OFF. Command fuel pump ON with scan tool. Is fuel pressure within 48-52 psi (334-375 kPa) while fuel pump is operating? If yes, go to next step. If no, go to «FUEL SYSTEM PRESSURE TEST (4.2L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE).
  8. Disconnect Crankshaft Position (CKP) sensor. Attempt to start engine. Does engine start and continue to run? If yes, go to step 11 . If no, go to next step.
  9. Inspect for the following: A collapsed air intake duct. A restricted air filter element. Spark plugs for being gas or coolant fouled. If spark plugs are fouled, determine what caused condition. An engine mechanical condition (worn timing chain, gears and low compression). A restricted exhaust system. Engine Coolant Temperature (ECT) sensor is not close to actual engine temperature. See «DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE»(ref-132531-S23800550162002012100000) or «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(ref-132531-S15140294882002012100000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article. Compare MAP/BARO parameters to another vehicle. Parameters should be close in value. See «DTC P0105: MAP SYSTEM PERFORMANCE»(ref-132531-S33534962272002012100000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article. TP sensor for being stuck in range. See «DTC P1221: EXCESSIVE DIFFERENCE BETWEEN THROTTLE POSITION SENSORS»(ref-132531-S14204156532002012900000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article. After repairs, go to step 12 .
  10. Repair Ignition 1 signal voltage circuit for an open or a short to ground. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. Replace fuse if necessary. After repairs, go to next step.
  11. Replace CKP sensor. After repairs, go to next step.
  12. Clear DTCs with scan tool. Turn OFF the ignition for 30 seconds. Attempt to start engine. Does engine start and continue to run? If yes, go to next step. If no, go to step 2 .
  13. Allow engine to reach operating temperature. Observe DTC information with scan tool. Are there any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-132531-S07878208602002012100000) in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article.

The Engine Cranks but Does Not Run diagnostic test is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic test directs the service technician to the appropriate system diagnosis. The Engine Cranks but Does Not Run diagnostic test assumes the following: The battery is completely charged, the cranking speed is within specification and there is adequate fuel in the fuel tank.

The number below refers to the step number in the diagnostic test.

  1. 5) This step determines if the fuel pump is operating electrically.
  1. Did you perform a Diagnostic System Check-Engine Controls? If yes, go to next step. If no, perform «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-137937-S42271286052002031300000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
  2. Turn ON the ignition, with the engine OFF. With a scan tool, observe the DTC information. Does the scan tool display DTCs P0230, P0335, P0336, P0601, P0602, P0604, P1626, P1631 or P1683? If yes, perform appropriate diagnostic test. See appropriate SELF-DIAGNOSTICS article. If no, go to next step.
  3. Attempt to start the engine. With a scan tool, monitor the Engine Speed parameter while the engine is cranking. Does the engine speed increment? If yes, go to next step. If no, go to DISTRIBUTOR IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  4. Monitor the Ignition 1 Signal Voltage parameter with a scan tool. Is the Ignition 1 Signal Voltage parameter at battery voltage. If yes, go to next step. If no, go to step 10 .
  5. With a scan tool, command the fuel pump ON. Does the fuel pump turn ON? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  6. Turn OFF the ignition. Disconnect a spark plug wire. Install the J 26792 Spark Tester to the spark plug wire. Attempt to start the engine. Does the spark tester spark? If yes, go to next step. If no, go to DISTRIBUTOR IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  7. Turn OFF the ignition. Disconnect the injector connector. Install the J 34730-375 Injector Test Lamp to an injector connector. Attempt to start the engine. Does the test light blink while the engine is cranking. If yes, go to next step. If no, go to «DTC P0200: FUEL INJECTOR CONTROL CIRCUIT»(ref-137937-S18600309342002031300000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
  8. Turn OFF the ignition. Install the J 34730-1A Fuel Pressure Gauge. Turn ON the ignition, with the engine OFF. With a scan tool, command the fuel pump ON. Is the fuel pressure 60-66 psi (414-455 kPa)? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  9. Inspect for the following conditions: Collapsed air intake duct. Restricted air filter element. Spark plugs for being gas or coolant fouled. If the spark plugs are fouled, determine what caused the condition. Engine mechanical condition (worn timing chain, gears and low compression). Restricted exhaust system. The Engine Coolant Temperature (ECT) sensor is not close to the actual engine temperature. See «DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE»(ref-137937-S23368886632002031300000) or «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(ref-137937-S15545525912002031300000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. Compare Manifold Absolute Pressure/Barometric Pressure (MAP/BARO) parameters to another vehicle. The parameters should be close in value. See «DTC P0106: MAP SYSTEM PERFORMANCE»(ref-137937-S01219711872002031300000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. The Throttle Position (TP) sensor for being stuck in range. See «DTC P0121: TP SENSOR PERFORMANCE»(ref-137937-S42948407422002031300000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. Did you find and correct the condition? If yes, go to step 11 . If no, fault is intermittent. See «INTERMITTENTS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__intermittents) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  10. Repair the ignition 1 signal voltage circuit for an open or a short to ground. Replace the fuse, if necessary. After repair is made, go to next step.
  11. With a scan tool, clear the DTCs. Attempt to start the engine. Does the engine start and continue to operate? If yes, go to next step. If no, go to step 2 .
  12. Idle the engine. Allow the engine to reach operating temperature. With a scan tool, observe the DTC information. Are any DTCs displayed? If yes, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-137937-S42609277872002031300000) in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. If no, go to next step.
  13. With a scan tool, review the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-137937-S42609277872002031300000) in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. If no, system is okay.

The Engine Cranks but Does Not Run diagnostic test is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic test directs the service technician to the appropriate system diagnosis. The Engine Cranks but Does Not Run diagnostic test assumes the following: The battery is completely charged, the cranking speed is within specification and there is adequate fuel in the fuel tank.

The number below refers to the step number in the diagnostic test.

  1. 6) This step determines if the fuel pump is operating electrically.
  1. Did you perform a Diagnostic System Check-Engine Controls? If yes, go to next step. If no, perform «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-137808-S13134129342002030800000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.
  2. Turn ON the ignition, with the engine OFF. With a scan tool, observe the DTC information. Does the scan tool display DTCs P0230, P0335, P0336, P0601, P0602, P0604, P1626, P1631 or P1683? If yes, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-137808-S26333189042002030800000) in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. If no, go to next step.
  3. Observe the DTC information in Passlock®. Does the scan tool display DTC B2960? If yes, diagnose DTC. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT. If no, go to next step.
  4. Attempt to start the engine. With a scan tool, monitor the Engine Speed parameter while the engine is cranking. Does the engine speed increment? If yes, go to next step. If no, go to DISTRIBUTOR IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  5. Monitor the Ignition 1 Signal Voltage parameter with a scan tool. Is the Ignition 1 Signal Voltage parameter at battery voltage. If yes, go to next step. If no, go to step 11 .
  6. With a scan tool, command the fuel pump ON. Does the fuel pump turn ON? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  7. Turn OFF the ignition. Disconnect a spark plug wire. Install the J 26792 Spark Tester to the spark plug wire. Attempt to start the engine. Does the spark tester spark? If yes, go to next step. If no, go to DISTRIBUTOR IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  8. Turn OFF the ignition. Disconnect the injector connector. Install the J 34730-375 Injector Test Lamp to an injector connector. Attempt to start the engine. Does the test light blink while the engine is cranking. If yes, go to next step. If no, go to «DTC P0200: FUEL INJECTOR CONTROL CIRCUIT»(ref-137808-S39559151202002030800000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.
  9. Turn OFF the ignition. Install the J 34730-1A Fuel Pressure Gauge. Turn ON the ignition, with the engine OFF. With a scan tool, command the fuel pump ON. Is the fuel pressure 60-66 psi (414-455 kPa)? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  10. Inspect for the following conditions: Collapsed air intake duct. Restricted air filter element. Spark plugs for being gas or coolant fouled. If the spark plugs are fouled, determine what caused the condition. Engine mechanical condition (worn timing chain, gears and low compression). Restricted exhaust system. The Engine Coolant Temperature (ECT) sensor is not close to the actual engine temperature. See «DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE»(ref-137808-S10852978322002030800000) or «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(ref-137808-S25387880802002030800000) in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. Compare Manifold Absolute Pressure/Barometric Pressure (MAP/BARO) parameters to another vehicle. The parameters should be close in value. See «DTC P0106: MAP SYSTEM PERFORMANCE»(ref-137808-S37148671312002030800000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. The throttle position (TP) sensor for being stuck in range. See «DTC P0121: TP SENSOR PERFORMANCE»(ref-137808-S35702216302002030800000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. Did you find and correct the condition? If yes, go to step 12 . If no, fault is intermittent. See «INTERMITTENTS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__intermittents) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  11. Repair the ignition 1 signal voltage circuit for an open or a short to ground. Replace the fuse, if necessary. After repair is made, go to next step.
  12. With a scan tool, clear the DTCs. Attempt to start the engine. Does the engine start and continue to operate? If yes, go to next step. If no, go to step 2 .
  13. Idle the engine. Allow the engine to reach operating temperature. With a scan tool, observe the DTC information. Are any DTCs displayed? If yes, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-137808-S26333189042002030800000) in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. If no, go to next step.
  14. With a scan tool, review the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-137808-S26333189042002030800000) in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. If no, system is okay.

The Engine Cranks but Does Not Run diagnostic test is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic test directs the service technician to the appropriate system diagnosis. The Engine Cranks but Does Not Run diagnostic test assumes the following: The battery is completely charged, the cranking speed is within specification and there is adequate fuel in the fuel tank.

The number below refers to the step number in the diagnostic test.

  1. 3) This step determines if the ignition relay is providing the listed fuses with voltage.
  2. 5) This step determines if the fuel pump is operating electrically.
  1. Did you perform a Diagnostic System Check-Engine Controls? If yes, go to next step. If no, perform «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-132892-S28924723212002020400000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article.
  2. Turn ON the ignition, with the engine OFF. With a scan tool, observe the DTC information. Does the scan tool display DTCs P0230, P0335, P0336, P0601, P0602, P0604, P1626, P1631 or P1683? If yes, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-132892-S06243123872002020400000) in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. If no, go to next step.
  3. Turn ON the ignition, with the engine OFF. Probe both sides of fuses ECM 1, INJ A and INJ B. Does the test light illuminate on both sides of all the fuses listed? If yes, go to next step. If no, go IGNITION RELAY DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  4. Attempt to start the engine. With a scan tool, monitor the Engine Speed parameter while the engine is cranking. Does the engine speed increment? If yes, go to next step. If no, go to DISTRIBUTOR IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  5. With a scan tool, command the fuel pump ON. Does the fuel pump turn ON? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  6. Turn OFF the ignition. Install the J 34730-1A Fuel Pressure Gauge. Turn ON the ignition, with the engine OFF. With a scan tool, command the fuel pump ON. Is the fuel pressure 60-66 psi (414-455 kPa)? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  7. Turn OFF the ignition. Disconnect a spark plug wire. Install the J 26792 Spark Tester to the spark plug wire. Attempt to start the engine. Does the spark tester spark? If yes, go to next step. If no, go to DISTRIBUTOR IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  8. Inspect for the following conditions: Collapsed air intake duct. Restricted air filter element. Spark plugs for being gas or coolant fouled. If the spark plugs are fouled, determine what caused the condition. Engine mechanical condition (worn timing chain, gears and low compression). Restricted exhaust system. The Engine Coolant Temperature (ECT) sensor is not close to the actual engine temperature. See «DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE»(ref-132892-S22212972552002020400000) or «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(ref-132892-S34619241402002020400000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. Compare Manifold Absolute Pressure/Barometric Pressure (MAP/BARO) parameters to another vehicle. The parameters should be close in value. See «DTC P0106: MAP SYSTEM PERFORMANCE»(ref-132892-S32657280792002020400000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. The throttle position (TP) sensor for being stuck in range. See «DTC P0121: TP SENSOR PERFORMANCE»(ref-132892-S03426346942002020500000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. Did you find and correct the condition? If yes, go to next step. If no, fault is intermittent. See INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.
  9. With a scan tool, clear the DTCs. Attempt to start the engine. Does the engine start and continue to operate? If yes, go to next step. If no, go to step 2 .
  10. Idle the engine. Allow the engine to reach operating temperature. With a scan tool, observe the DTC information. Are any DTCs displayed? If yes, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-132892-S06243123872002020400000) in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. If no, go to next step.
  11. With a scan tool, review the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-132892-S06243123872002020400000) in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. If no, system is okay.

Ensure the battery is completely charged and the engine cranking speed is within specification. Ensure there is adequate fuel in the fuel tank.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 4 You may need to connect a battery charger to the battery for this step. If the battery state of charge is low, the scan tool may reset during the cranking test.
  2. 5 This step tests the ignition relay for proper operation. The ignition relay supplies voltage to the injectors and the ignition coils. When the ignition relay is not operating properly, a no start condition occurs. If the test light does not illuminate, this indicates the ignition relay is not suppling a voltage to the fuses.
  1. Perform «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-control-system-self-diagnostics-48l-53l-60l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C" & "K" SERIES TRUCKS article. After performing DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS, go to next step.
  2. Crank the engine for 15 seconds. Does the scan tool display any DTCs that failed this ignition? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-control-system-self-diagnostics-48l-53l-60l) in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C" & "K" SERIES TRUCKS article. If no, go to next step.
  3. Using scan tool, check the Body Control Module (BCM) for DTCs related to the Vehicle Theft Deterrent (VTD) system. Does the scan tool display any BCM VTD DTCs? If yes, perform DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT. If no, go to next step.
  4. Using scan tool, monitor the engine speed while cranking the engine. Is engine RPM indicated on the scan tool? If yes, go to next step. If no, see ELECTRONIC IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  5. Turn ignition switch to ON position. Using a test light connected to ground, probe both sides of fuses INJR A, INJR B and ECM I, located in the underhood electrical center. Does the test light illuminate on both sides of all 3 fuses? If yes, go to next step. If no, see IGNITION RELAY DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  6. Using the scan tool, monitor the Engine Coolant Temperature (ECT) parameter. Is the ECT on the scan tool close to the actual engine temperature? If yes, go to next step. If no, see «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-control-system-self-diagnostics-48l-53l-60l) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C" & "K" SERIES TRUCKS article.
  7. Using the scan tool, enable the fuel pump. Does the fuel pump operate? If yes, go to next step. If no, see FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  8. Turn ignition switch to OFF position. Release fuel pressure and install a fuel pressure gauge. See «FUEL SYSTEM PRESSURE RELEASE (4.8L, 5.3L, 6.0L & 8.1L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). The fuel pump operates for about 2 seconds when the ignition switch is turned to the ON position. The fuel pressure must be observed when the fuel pump is operating. Turn ignition switch to ON position. Observe the fuel pressure while the fuel pump is operating. Is the fuel pressure 55-62 psi (379-427 kPa)? If yes, go to next step. If no, diagnose fuel system. See FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS (GASOLINE).
  9. Perform the following checks: Check air duct between 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 diagnostic procedure for TP sensor DTCs. See «DTC P0121: TP SENSOR PERFORMANCE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-control-system-self-diagnostics-48l-53l-60l) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C" & "K" SERIES TRUCKS article. A malfunctioning Mass Airflow (MAF) sensor may cause a no start or a stall after a start. If you suspect this, disconnect the MAF sensor. The PCM will default to the speed density in order to calculate the engine load and the intake air flow. If disconnecting the MAF sensor corrects the condition and the connections are OK, replace the MAF sensor. See MASS AIRFLOW SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - SIERRA & SILVERADO article. Check for fouled spark plugs. If fouled, determine cause and repair as necessary. Check for possible engine mechanical failure causing a no-start condition, such as timing chain or low compression. Compare the MAP/BARO parameters to another vehicle. The parameter values should be close to each other. Did you find and correct the condition? If yes, go to next step. If no, see «HARD START»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes) under SYMPTOMS (GASOLINE) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  10. Using scan tool, clear DTCs. Attempt to start engine. Does engine start and continue to run? If yes, go to next step. If no, go to step 2 .
  11. Start and idle engine until normal operating temperature is reached. Using scan tool, check for DTCs. If any DTCs are set, diagnose DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-control-system-self-diagnostics-48l-53l-60l) in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C" & "K" SERIES TRUCKS article. If no DTCs are set, go to next step.
  12. Using scan tool, select CAPTURE INFO and REVIEW INFO functions. If any DTCs are set that have not been diagnosed, diagnose DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-control-system-self-diagnostics-48l-53l-60l) in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C" & "K" SERIES TRUCKS article. If no DTCs are set, system is okay.

Inspect for the following conditions

  1. The Mass Airflow (MAF) is compared to a calculated MAF based upon the Manifold Absolute Pressure (MAP), the Throttle Position (TP), and the engine RPM. A skewed or unresponsive MAP sensor at key ON will cause the predicted airflow value to be inaccurate. Compare the MAP and TP readings to that of a known good vehicle.
  2. Inspect for a faulty Engine Coolant Temperature (ECT) sensor. Use a scan tool in order to compare the ECT with the Intake Air Temperature (IAT) on a completely cooled engine. The ECT should be within 5°F (3°C) of the IAT.
  3. For an intermittent condition, diagnose by symptom. See «SYMPTOMS (GASOLINE)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__symptoms-gasoline) in TROUBLE SHOOTING - NO CODES - TRUCKS article.

The Engine Cranks but Does Not Run diagnostic test is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic test directs the service technician to the appropriate system diagnosis. The Engine Cranks but Does Not Run diagnostic test assumes the following: The battery is completely charged, the cranking speed is within specification and there is adequate fuel in the fuel tank.

The number below refers to the step number in the diagnostic test.

  1. 2) If the engine starts, the problem could be intermittent. Basic engine mechanical problems, the Vehicle Theft Deterrent (VTD) system (if equipped), and poor connections could cause a no-start condition.
  2. 3) This step will determine if the cause of the no start or start and stall is related to the VTD.
  3. 4) If the signal is over 2.5 volts, the engine may be in the clear flood mode which will cause starting problems.
  4. 5) If the engine coolant sensor is below -22°F (-30°C), the PCM provides fuel for this extremely cold temperature which will severely flood the engine.
  5. 6) Voltage at the spark plug is checked using the spark plug tester tool. No spark indicates a basic ignition problem.
  6. 7) This test will determine if there is fuel pressure at the fuel injection unit and holding steady.
  7. 8) Use the injector test light in order to test the injector circuits. A blinking lamp indicates that the PCM is controlling the injector.

Note. Before clearing the DTCs, use the scan tool Capture Info. to save the Freeze Frame and the Failure Records for reference. The control modules data is deleted once the Clear Info function is used.

  1. Did you perform a Diagnostic System Check-Engine Controls? If yes, go to next step. If no, perform «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-138116-S40610776842002032000000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 5.0L & 5.7L CHEVY EXPRESS & SAVANA article.
  2. Attempt to start the engine. Does the engine start and continue to run? If yes, fault is intermittent. See «INTERMITTENTS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__intermittents) in TROUBLE SHOOTING - NO CODES - TRUCKS article. If no, go to next step.
  3. Install a scan tool. Monitor the VTD fuel disables parameter. Crank the engine. Does the VTD fuel disables parameter display active while you crank the engine? If yes, perform THEFT DETERRENT SYSTEM DIAGNOSTIC SYSTEM CHECK. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.
  4. Monitor the Throttle Position (TP) sensor on the scan tool. With the throttle closed, is the TP sensor more than 2.5 volts? If yes, go to «DTC P0121: TP SENSOR PERFORMANCE»(ref-138116-S07326966892002032000000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 5.0L & 5.7L CHEVY EXPRESS & SAVANA article. If no, go to next step.
  5. Monitor the ECT sensor on the scan tool. Is the ECT sensor below -22°F (-30°C)? If yes, go to «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(ref-138116-S13159537662002032000000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 5.0L & 5.7L CHEVY EXPRESS & SAVANA article. If no, go to next step.
  6. Check for spark at two spark plug wires using the J-26792 Spark Tester. Is spark present at both spark plug wires? If yes, go to next step. If no, go to ELECTRONIC IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS article.
  7. Reconnect the spark plug wires. Turn OFF the ignition. Connect the J 34730-1A Fuel Pressure Gauge. Turn ON the ignition, with the engine OFF. Is the fuel pressure 55-60 psi (379-413 kPa)? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  8. Disconnect the injector connector at the intake manifold. Install the J 34730-375 Injector Test Lamp into each injector circuit one at a time. Crank the engine with the injector test light in each circuit. Does the injector test light flash for each injector circuit? If yes, go to Diagnostic Aids. See «DIAGNOSTIC AIDS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . If no, go to «DTC P0200: FUEL INJECTOR CONTROL CIRCUIT»(ref-138116-S06454471742002032000000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 5.0L & 5.7L CHEVY EXPRESS & SAVANA article.

If no trouble is found in the fuel pump circuit or the ignition system and the cause of an Engine Cranks But Will Not Run has not been found, check the following conditions

  1. Perform the Fuel Injector Coil Test. See FUEL INJECTOR COIL TEST under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  2. An after-market vehicle theft deterrent system could cause a start then stall or a no-start condition.
  3. Fouled spark plugs.
  4. An Exhaust Gas Recirculation (EGR) valve stuck open.
  5. Water or foreign material in the fuel system.
  6. A grounded or intermittently grounded Ignition Control (IC) signal circuit.
  7. Restricted exhaust system.
  8. Check the following ignition components: A grounded tach circuit. Worn distributor cap. Worn distributor rotor. Check ignition wires by lightly spraying them with water in order to identify intermittent no-starts.
  9. Check the following mechanical components: Cylinder valve timing. Loose or broken timing chain. Low compression. Worn camshaft lobes. Bent or burned intake or exhaust valves.

The PCM has integrated circuits that are fault protected, therefore, if a circuit has failed, the integrated circuit may not be damaged. If that is the case, then the system will keep the circuit open until the condition has been corrected. Afterwards, reinstall the PCM and check the circuit. Replace the PCM only if the circuit is still inoperative. An intermittent may be caused by any of the following conditions: A poor connection. Rubbed through wire insulation. A broken wire inside the insulation. Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Repair as necessary.

Ensure that battery condition and engine cranking speed is okay. Ensure that quantity and quality of fuel is okay and glow plug system is operating properly. If diesel fuel system is contaminated with gasoline, purge fuel system. See FUEL SYSTEM CLEANING under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 6 This step checks for proper cranking speed. See «DIAGNOSTIC AIDS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .
  2. 8 This step will check ground wire on injection pump. Wire is located on top of pump.
  3. 12 This step will determine if injection pump or wiring is at fault.
  4. 13 This step will determine if fuel injection control voltage is present by probing at Black/Gray 4-pin connector jumper harness instead of at 6-pin pump connector.
  1. Perform OBD system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-139779-S23178353562002050900000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.5L CAB & CHASSIS, CHEVY EXPRESS & SAVANA 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 22 .
  3. Check fuel level in tank. If fuel level is okay, go to next step. If fuel level is not okay, go to step 22 .
  4. Check quality of fuel. If fuel quality is okay, go to next step. If fuel quality is not okay, go to step 22 .
  5. Check glow plug system operation. Go to GLOW PLUG SYSTEM DIAGNOSIS under FUEL SYSTEM (DIESEL) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article. If glow plug operation is okay, go to next step. If glow plug operation is not okay, go to step 22 .
  6. Check for proper engine cranking speed. See «DIAGNOSTIC AIDS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . If engine cranking speed is okay, go to next step. If engine cranking speed is not okay, go to step 22 .
  7. Check fuel supply system. Go to FUEL SYSTEM DIAGNOSIS (6.5L) under FUEL SYSTEM (DIESEL) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article. If fuel system is okay, go to next step. If fuel system is not okay, go to step 22 .
  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 22 .
  9. Install scan tool. Using scan tool, check for any data. If data is displayed, go to next step. If data is not displayed, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS in APPROPRIATE BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  10. Using scan tool, monitor VTD Fuel Disabled parameter on Powertrain Engine Data 1 list. Crank engine. If VTD Fuel Disabled parameter displays ACTIVE while engine is cranked, diagnose VTD system. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT. If VTD Fuel Disabled parameter 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 injection line, injection system is okay. If fuel does not flow from each injection 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 4-pin connector. Using DVOM, measure voltage between ground and fuel injector control circuit at harness connector while cranking engine. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If voltage is 1.2 volts or more, go to next step. If voltage is less than 1.2 volts, go to step 17 .
  14. With fuel solenoid driver 4-pin connector still disconnected, probe solenoid closure ground circuit at harness connector with test light connected to battery voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 18 .
  15. Turn ignition on. Ensure fuel solenoid driver 4-pin connector is still disconnected. Using test light connected to ground, probe ignition feed circuit at fuel solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 20 .
  16. Replace fuel injection pump. After repairs, go to step 24 .
  17. Check for open or short to ground in fuel injection control circuit between fuel solenoid driver and PCM. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 19 .
  18. Check closure signal ground circuit for open between fuel solenoid driver and PCM. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to next step.
  19. Check for poor connections at fuel solenoid driver and PCM harness connectors. Repair as necessary. After repairs, go to step 21 . If connections are okay, go to step 23 .
  20. Repair open in Ignition 1 voltage circuit. After repairs, go to step 24 .
  21. Repair circuit as necessary. After repairs, go to step 24 .
  22. Repair as necessary. After repairs, go to step 24 .
  23. Replace PCM. Perform PCM relearn procedures. See «PROGRAMMING»(ref-139779-S22575193592002050900000) in SELF-DIAGNOSTICS - 6.5L CAB & CHASSIS, CHEVY EXPRESS & SAVANA article. After repairs, go to next step.
  24. 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 .
  25. Using scan tool, select Capture Info, Review Info function. If any other DTCs are set that have not been diagnosed, diagnose DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-139779-S39258880492002050900000) in SELF-DIAGNOSTICS - 6.5L CAB & CHASSIS, CHEVY EXPRESS & SAVANA article. If DTCs are not set, system is okay.

If no fault is found and cause of NO-START - ENGINE CRANKS OKAY condition has not been found, check for the following conditions

  1. Proper cranking speed, 100 RPMs (cold) or 180 RPMs (hot). Scan tool can be used to check cranking speed by pulling FUEL SOL fuse and monitoring engine speed on scan tool while cranking.
  2. Water or foreign material in fuel system.
  3. Base engine mechanical fault.
  4. If Crankshaft Position (CKP) sensor and optical/fuel temperature sensor are disconnected or malfunctioning at same time, a NO-START - ENGINE CRANKS OKAY condition will exist.

Ensure batteries are completely charged, cranking speed is within specifications and that there is adequate fuel in fuel tanks.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 4 This step tests for Ignition 1 voltage supply to engine control module (ECM).
  2. 6 This step tests 12-volt reference circuit to CKP sensor and CMP sensor. 12-volt reference circuit for CKP sensor and CMP sensor is connected internally within ECM. If 12-volt reference circuit is shorted to ground, engine will not start and no engine speed will be indicated on scan tool.
  3. 7 If there is high resistance in signal or low reference circuits of CKP sensor, Engine Speed parameter on scan tool will display a value more than zero. It will not be an accurate measure of engine speed, and can cause an NO-START - ENGINE CRANKS OKAY condition.
  4. 8 If there is fuel in engine oil, fuel may be leaking from fuel injector or fuel injection pump into crankcase.
  5. 9 If fuel system will not even briefly prime to 10 psi and will not start, check valve in fuel filter/heater element housing is stuck open.
  6. 10 This step determines if fuel system is bleeding down causing a no-start. Fuel pressure will slowly drop to zero psi, but should still be above 8 psi for 10 seconds after pressurizing fuel system.
  7. 12 This step determines if problem is a stuck open or broken fuel injector. If fuel vapors come out of any glow plug holes, excessive fuel is being sent into a cylinder, and not being distributed to all fuel injectors.
  8. 13 The engine will not run without an actual fuel rail pressure more than 1450 psi (10 MPa).
  9. 15 If no-start condition takes place in cold operating temperatures, 35-40°F (2-4°C) or colder, a glow plug system failure may cause no-start condition.
  10. 17 In some cases, no compression, possibly with excessive fuel, in a single cylinder can cause a no-start.
  1. Perform OBD system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-138411-S24056483272002041200000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO article. After performing diagnostic system check, go to next step.
  2. Turn ignition on, with engine off. Check for DTCs. If DTC P0088, P0089, P0090, P0335, P0336, P0340, P0370, P0374, P0380, P0601, P0602, P0603, P0604, P0611, P0612, P1621, P1626, P1631, P1683, or U1800 is set, perform appropriate diagnostic procedure for DTC set. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-138411-S02438938112002041200000) in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO article. If no DTCs are set, go to next step.
  3. If customer's concern is with a fuel smell or fuel leak, go to «FUEL LEAKS INSIDE OF ENGINE (6.6L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-leaks-inside-of-engine-66l) or «FUEL LEAKS OUTSIDE OF ENGINE (6.6L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-leaks-outside-of-engine-66l) under FUEL SYSTEM (DIESEL) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article. If a fuel smell or fuel leak concern is not present, go to next step.
  4. Turn ignition on. Using scan tool, observe Actual Fuel Rail Pressure parameter. If pressure is 159-203 psi (1100-1400 kPa), go to next step. If pressure is not as specified, go to step 18 .
  5. Using scan tool, observe Ignition 1 signal parameter. If Ignition 1 signal parameter indicates battery voltage, go to next step. If Ignition 1 signal parameter does not indicate battery voltage, go to step 24 .
  6. Attempt to start engine. Using scan tool, observe Engine Speed parameter while cranking engine. If Engine Speed parameter is more than zero RPM, go to next step. If Engine Speed parameter is not more than zero RPM, go to step 19 .
  7. Test CKP sensor signal and low reference circuits for high resistance. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. After repairs, go to step 34 . If CKP sensor signal and low reference circuits are okay, go to next step.
  8. Check for excessive fuel in engine oil, contaminated fuel and check fuel specific gravity. After repairs, go to step 34 . If engine oil, fuel and fuel specific gravity are okay, go to next step.
  9. Install vacuum gauge to fuel system service port on right front side of engine. Attempt to hand prime fuel manager 30 times or until fuel pressure is 8 psi (55 kPa). If fuel system is able to be primed to 8 psi (55 kPa), go to next step. If fuel system is not able to be primed to 8 psi (55 kPa), go to step 31 .
  10. If system pressure is maintained at more than 2.0 psi (13.8 kPa) for more than 2 minutes, go to next step. If system is not able to maintain more than 2.0 psi (13.8 kPa) for more than 2 minutes, go to step 14 .
  11. Check engine compression. For compression specifications, see «SERVICE & ADJUSTMENT SPECIFICATIONS - TRUCKS»(/gmc/yukon-denali/gmt800-1999-2006/remont/specifications/#engine-controls-service-adjustment-specifications) article. Repair engine as necessary. After repairs, go to step 34 . If engine compression is within specification, go to next step.
  12. If any cylinders emitted fuel vapor during engine compression test, go to step 28 . If no fuel vapor was emitted from cylinders during engine compression test, go to next step.
  13. Crank engine for 15 seconds. Using scan tool, observe Actual Fuel Rail Pressure parameter. If Actual Fuel Rail Pressure parameter is more than 1450 psi (10 MPa), go to step 15 . If Actual Fuel Rail Pressure parameter is 1450 psi (10 MPa) or less, go to next step.
  14. Reprime fuel manager to 10 psi. Attempt to start engine while prime is still above 8 psi (55 kPa). If engine now starts, go to «FUEL SYSTEM DIAGNOSIS - PICKUP (6.6L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-system-diagnosis-pickup-66l) or «FUEL SYSTEM DIAGNOSIS - CAB & CHASSIS (6.6L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-system-diagnosis-cab) under FUEL SYSTEM (DIESEL) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article. If engine does not start, go to «FUEL SYSTEM DIAGNOSIS - HIGH PRESSURE SIDE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-system-diagnosis-high-pressure) under FUEL SYSTEM (DIESEL) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  15. Using scan tool, observe Glow Plug System Type parameter. If Glow Plug System Type indicates Federal, go to next step. If Glow Plug System Type does not indicate Federal, go to step 17 .
  16. Turn ignition off. Connect a test light to a glow plug harness connector on one side of engine. Turn ignition on, with engine off. If test light illuminates and then goes off, go to next step. If test light does not illuminate and then go off, go to «GLOW PLUG SYSTEM DIAGNOSIS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__glow-plug-system-diagnosis-65l) under FUEL SYSTEM (DIESEL) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  17. Check for the following conditions: Plugged air filter. Collapsed air intake duct. Inoperative fuel heater. If customer's concern is that engine will not start when ambient temperatures are less than 35-40°F (2-4°C), go to «FUEL HEATER INOPERATIVE DIAGNOSIS (6.6L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-heater-inoperative-diagnosis-66l) under FUEL SYSTEM (DIESEL) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article. Restricted exhaust system. Repair as necessary. After repairs, go to step 34 . If no repairs are necessary, go to «DIAGNOSTIC AIDS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .
  18. Disconnect fuel rail pressure sensor. Using scan tool, observe Actual Fuel Rail Pressure parameter on scan tool. If Actual Fuel Rail Pressure parameter is more than 25,381 psi (175 MPa), go to step 23 . If Actual Fuel Rail Pressure parameter is 25,381 psi (175 MPa) or less, go to step 22 .
  19. Turn ignition off. Disconnect Crankshaft Position (CKP) sensor. Turn ignition on, with engine off. Using a DVOM connected to ground, probe 12-volt reference circuit at CKP sensor. If voltage is more than 10 volts, go to step 29 . If voltage is 10 volts or less, go to next step.
  20. Turn ignition off. Disconnect Camshaft Position (CMP) sensor. Turn ignition on, with engine off. Using a DVOM connected to ground, probe 12-volt reference circuit of CMP sensor. If voltage is more than 10 volts, go to step 30 . If voltage is 10 volts or less, go to next step.
  21. Check 12-volt reference circuit to CKP sensor and CMP sensor for a short to ground. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. Repair as necessary. After repairs, go to step 34 . If no repairs are necessary, go to step 33 .
  22. Check fuel rail pressure sensor signal circuit for a short to ground. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. Repair as necessary. After repairs, go to step 34 . If no repairs are necessary, go to step 33 .
  23. Check fuel rail pressure sensor circuits for high resistance. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. Repair as necessary. After repairs, go to step 34 . If no repairs are necessary, go to step 25 .
  24. Check Ignition 1 voltage circuit of ECM for a short to ground, high resistance or an open. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. Repair as necessary. After repairs, go to step 34 . If no repairs are necessary, go to step 26 .
  25. Check for an intermittent or for a poor connection at fuel rail pressure sensor. Repair as necessary. After repairs, go to step 34 . If no repairs are necessary, go to step 32 .
  26. Clean and tighten ECM shared ground. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. Repair as necessary. After repairs, attempt to start engine. If engine starts, go to step 34 . If engine does not start, go to next step.
  27. Check for an intermittent and for a poor connection at ECM. Repair as necessary. After repairs, go to step 34 . If no repairs are necessary, go to step 33
  28. Replace fuel injectors on affected cylinders. After repairs, go to step 34 .
  29. Replace CKP sensor. After repairs, go to step 34 .
  30. Replace CMP sensor. After repairs, go to step 34 .
  31. Replace fuel filter/heater element housing. After repairs, go to step 34 .
  32. Replace fuel rail pressure sensor. After repairs, go to step 34 .
  33. Replace ECM. Perform ECM relearn procedures. See «PROGRAMMING»(ref-138411-S27281177062002041200000) in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO article. After repairs, go to next step.
  34. Clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, repeat step 2
  35. Allow engine to idle until normal operating temperature is reached. Check for DTCs. If any DTCs are set, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-138411-S02438938112002041200000) in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO article. If no DTCs are set, system is okay.

If cause of NO-START - ENGINE CRANKS OKAY symptom has not been found, inspect for following conditions

  1. Hard starting only in cold ambient temperatures.
  2. Correct cranking speed is 100 RPM cold and 180 RPM hot. A scan tool can be used to inspect cranking speed by pulling Ignition 1 relay and monitoring engine speed on scan tool while cranking.
  3. Water or foreign material in fuel system.
  4. A base engine mechanical fault.
  5. If Crankshaft Position (CKP) sensor and Camshaft Position (CMP) sensor are disconnected or malfunctioning at the same time, a NO-START - ENGINE CRANKS OKAY condition will exist.

NO-START - ENGINE CRANKS OKAY (8.1L)

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

Ensure battery is completely charged and that cranking speed is within specifications. Ensure there is adequate fuel in fuel tank

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 3 This step determines if ignition relay is providing ECM 1, ETC, INJ A and INJ B fuses with voltage.
  2. 5 This step determines if fuel pump is operating electrically.
  1. Perform OBD system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-138305-S37770098362002040400000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L "C", "G" & "K" SERIES TRUCKS article. After performing diagnostic system check, go to next step.
  2. Turn ignition on, with engine OFF. Check for DTCs. If DTC P0230, P0335, P0336, P0601, P0602, P0604, P0606, P1626, P1631 or P1683 is set, perform appropriate diagnostic procedure for DTC set. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-138305-S40253083952002040400000) in SELF-DIAGNOSTICS - 8.1L "C", "G" & "K" SERIES TRUCKS article. If no DTCs are set, go to next step.
  3. Turn ignition on, with engine OFF. Using test light connected to ground, probe both sides of ECM 1, ETC, INJ A and INJ B fuses. If test light illuminates on both sides of all fuses, go to next step. If test light does not illuminate on both sides of all fuses, go to «IGNITION RELAY DIAGNOSIS (8.1L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__ignition-relay-diagnosis-43l) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  4. Turn ignition off. Disconnect a spark plug wire. Install Spark Tester (J 26792) to spark plug wire. Attempt to start engine. If spark tester indicates a good spark, go to next step. If spark tester does not indicate a good spark, go to «ELECTRONIC IGNITION SYSTEM DIAGNOSIS (8.1L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__electronic-ignition-system-diagnosis-48l-53l) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  5. Using scan tool, command fuel pump ON. If fuel pump operates, go to next step. If fuel pump does not operate, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  6. Turn ignition off. Install fuel pressure gauge. Turn ignition on, with engine off. Using scan tool, command fuel pump ON. If fuel pressure is 55-62 psi (384-425 kPa) while fuel pump is operating, go to next step. If fuel pressure is not as specified, go to «FUEL SYSTEM PRESSURE TEST (4.8L, 5.3L, 6.0L & 8.1L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE).
  7. Turn ignition off. Disconnect an injector connector. Install Injector Test Light (J 34730-405) to injector connector. Attempt to start engine. If test light blinks while engine is cranking, go to next step. If test light does not blink while cranking, go to «DTC P0200: FUEL INJECTOR CONTROL CIRCUIT»(ref-138305-S34606889602002040400000) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 8.1L "C", "G" & "K" SERIES TRUCKS article.
  8. Check for the following conditions: Collapsed air intake duct. Restricted air filter element. Spark plugs for being gas or coolant fouled. If spark plugs are fouled, determine what caused condition. Engine mechanical condition, worn timing chain and gears, low compression, etc. Restricted exhaust system. ECT sensor is NOT close to actual engine temperature. Compare MAP/barometric pressure (BARO) parameters to another vehicle. The parameters should be close in value. After repairs, go to next step. If no problems are found, go to «DIAGNOSTIC AIDS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) .
  9. Clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not run, repeat step 2 .
  10. Allow engine to idle and reach operating temperature. Check for DTCs. If any DTCs are set, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-138305-S40253083952002040400000) in SELF-DIAGNOSTICS - 8.1L "C", "G" & "K" SERIES TRUCKS article. If no DTCs are set, go to next step.
  11. Using scan tool, review stored information, Capture Info. If scan tool displays any DTCs that have not been diagnosed, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-138305-S40253083952002040400000) in SELF-DIAGNOSTICS - 8.1L "C", "G" & "K" SERIES TRUCKS article. If no DTCs are set, system is okay.

Inspect for the following conditions

  1. Mass airflow (MAF) is compared to a calculated MAF based upon Manifold Absolute Pressure (MAP), Throttle Position (TP), and engine RPM readings. A skewed or unresponsive MAP sensor at KEY ON will cause predicted airflow value to be inaccurate. Compare MAP and TP sensor values to that of a known good vehicle.
  2. Faulty ECT sensor. Using a scan tool, compare engine coolant temperature with Intake Air Temperature (IAT) on a completely cool engine. ECT should be within 5°F (3°C) of intake air temperature. For an intermittent condition, go to «INTERMITTENTS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__intermittents) in TROUBLE SHOOTING - NO CODES - TRUCKS article.

FUEL SYSTEM PRESSURE RELEASE

  1. Using scan tool, attempt to communicate with Alternative Fuel Electronic Control Unit (AF ECU). If communication is possible, go to next step. If communication is not possible and system check has been performed, go to step 7 .
  2. Read and record any AF ECU DTCs. Go to next step.
  3. Clear all AF ECU DTCs. Turn ignition off. Go to next step.
  4. Start engine. Ensure vehicle is operating on CNG by noting if fuel indicator light (located on fuel gauge select switch) is off and Natural Gas Operation (NGO) in scan tool data is enabled. If vehicle is operating on CNG, go to next step. If vehicle does not start or is not operating on CNG, go to step 7 .
  5. Using scan tool, select High Pressure Lock-Off (HPL) output control. Go to next step.
  6. Monitor Fuel Pressure Sensor (FPS) data. While vehicle is operating on CNG, use scan tool to close HPL. If FPS data does not change, go to next step. When engine stalls or changes to gasoline operation, turn ignition off. Remove CNG fuse (20-amp) located in underhood fuse block. Slowly open fuel system fittings to vent remaining pressure.
  7. Remove fuel tank cover. Close manual lock down screw on HPL by rotating Allen screw clockwise until fully seated. Go to next step.
  8. Turn ignition off. Disconnect negative battery cable. Ensure vehicle is in a well ventilated area, away from sparks and flame. Go to next step.
  9. Slowly open fuel line fitting at Low Pressure Lock-Off (LPL) inlet port. Do not remove fitting. Go to next step.
  10. If fuel is not venting, relieve fuel line tension by pulling line away from LPL. Go to next step.
  11. After fuel has stopped venting, slowly loosen fuel line fitting at High Pressure Regulator (HPR) inlet. Do not remove fitting. Fuel pressure relief is complete when fuel line at HPR inlet stops venting. After repair, replace "O" rings at all fittings that were loosened. Tighten all loosened fittings to specification. Open manual lock down screw counterclockwise to fully seated position.

BASIC FUEL SYSTEM CHECKS (DIESEL)

Note. For diesel fuel system and component diagnosis, see FUEL SYSTEM (DIESEL) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.

WARNINGRemove fuel tank cap and release fuel system pressure before servicing any fuel injection-related components. After releasing fuel system pressure, a small amount of fuel may be released when servicing fuel lines, fuel pump or fuel connections. Cover the fuel system components with a shop towel before disconnection. DO NOT allow fuel to contact engine or electrical components.
CAUTIONFuel system is under pressure. Pressure must be released prior to servicing fuel system.

Loosen retaining bolt on intake manifold sight shield at top of engine. Remove intake manifold sight shield from top of engine. Disconnect negative battery cable. Loosen fuel filler cap. Install Fuel Pressure Gauge (J-34730-1A) on fuel pressure connector of fuel rail. Wrap a shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage. Place gauge bleed hose in container. Open bleed valve to release fuel pressure.

FUEL SYSTEM PRESSURE TEST (2.2L & 3.0L VUE)

Install a Fuel Pressure Gauge (SA9127E) to fuel service test port. Turn ignition on, with engine off. Using a scan tool, command fuel pump on. Fuel pressure should be 50-60 psi (3.5-4.2 kg/cm 2 ). If fuel pressure is not as specified, diagnose fuel system.

  1. Perform OBD system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-138342-S08198199552002040800000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Does fuel pump operate? If yes, go to next step. If no, diagnose fuel pump electrical circuit.
  3. Turn ignition off. Turn off all accessories Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Install Fuel Pressure Gauge (J-34730-FF). Turn ignition on, with engine off. Command fuel pump ON with scan tool. It may be necessary to command the fuel pump on a few times in order to obtain the highest possible fuel pressure. Observe fuel pressure gauge with fuel pump commanded ON. Is fuel pressure 56-62 psi (386-427 kPa)? If yes, go to next step. If no, go to step 9 .
  4. Monitor the fuel pressure gauge for one minute. If fuel pressure decreases more than 5 psi (34 kPa) in one minute, go to step 7 . If fuel pressure does not decrease more than 5 psi (34 kPa) in one minute, go to next step.
  5. Relieve fuel pressure to 10 psi (69 kPa). Monitor fuel pressure gauge for 5 minutes. Does fuel pressure decrease by more than 2 psi (14 kPa)? If yes, go to step 17 . If no, go to next step.
  6. Operate the vehicle within the conditions to reproduce the original symptoms. Monitor O2 and fuel trim parameters with a scan tool. Do the scan tool parameters indicate a lean condition? If yes, go to step 12 . If no, see «INTERMITTENTS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__intermittents) in TROUBLE SHOOTING - NO CODES - 2.2L SONOMA & S10 PICKUP article.
  7. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Disconnect fuel feed hose from fuel rail. Install Fuel Line Shut-Off Adapter (J-37287) between fuel hose and fuel rail. Open valve on fuel pipe shut-off adapter. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Bleed air from fuel pressure gauge. Command fuel pump ON and then OFF with scan tool. Close fuel feed pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does the fuel pressure remain constant? If yes, go to next step. If no, go to step 15 .
  8. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Open fuel feed pipe shut-off valve. Raise and support vehicle. Disconnect fuel return pipe from fuel filter. Install Fuel Line Shut-Off Adapter (J-37287) between fuel return pipe and fuel filter. Open fuel return pipe shut-off valve. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Bleed air from fuel pressure gauge. Command fuel pump ON and then OFF with a scan tool. Close the fuel return pipe shut-off valve. Monitor the fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to step 16 . If no, go to step 17 .
  9. Is the fuel pressure greater than 62 psi (427 kPa)? If no, go to step 11 . If yes, go to next step.
  10. Inspect the fuel return pipe and for a restriction. Repair as necessary, then go to step 18 . If repair is not necessary, go to step 16 .
  11. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Raise and support vehicle. Disconnect fuel return pipe from fuel filter. Install Fuel Line Shut-Off Adapter (J-37287) between fuel return pipe and fuel filter. Open the valve in the fuel pipe shut-off adapter. Turn ignition on, with engine off. Bleed air from the fuel pressure gauge. Monitor fuel pressure gauge. DO NOT allow fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage fuel system. Command fuel pump ON with a scan tool. Slowly close the valve in the fuel return pipe shut-off adapter, while the fuel pump is operating. Does the fuel pressure increase to greater than 62 psi (427 kPa)? If yes, go to step 15 . If no, go to next step.
  12. Inspect for a restricted fuel filter or fuel feed pipe. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
  13. Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
  14. Remove fuel sender assembly. Inspect fuel pump flex hose for damage, in-tank fuel pump harness connectors for poor connections, fuel strainer for a restriction or fuel tank for contaminants. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 17 .
  15. Turn ignition off. Raise fuel rail assembly with fuel pipe connected. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Locate and replace leaking fuel injector. After repairs, go to step 18 .
  16. Replace fuel filter. After replacing fuel filter, go to step 18 .
  17. Replace fuel sender. After replacing fuel sender, go to next step.
  18. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step 3 .
  1. Perform OBD system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in «SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE»(ref-140805) or «SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS»(ref-140049) . 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 RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. Place fuel pressure gauge bleed hose into container. Connect negative battery cable. Turn ignition on. Bleed air from fuel pressure gauge. Using scan tool, command fuel pump on. Observe fuel pressure with fuel pump running. Fuel pressure should be 52-59 psi (3.7-4.1 kg/cm 2 ). If fuel pressure is within specification, go to step 6 . If fuel pressure is not within specification, go to next step.
  3. If indicated fuel pressure is greater than 59 psi (4.1 kg/cm 2 ), go to step 14 . If indicated fuel pressure is not greater than 59 psi (4.1 kg/cm 2 ), go to next step.
  4. Check fuel system for leaks. Repair as necessary. After repairs, go to step 21 . If no leaks are present, go to next step.
  5. If indicated fuel pressure is greater than zero psi, go to step 7 . If indicated fuel pressure is not greater than zero psi, go to step 16 .
  6. Monitor fuel pressure. If fuel pressure decreases more than 5 psi (.4 kg/cm 2 ) in 10 minutes, go to next step. If pressure does not decrease more than 5 psi (.4 kg/cm 2 ) in 10 minutes, go to step 9 .
  7. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Connect Fuel Pipe Shutoff Adapters (J-37287) between fuel feed pipe and fuel return pipe at fuel rail. Open fuel feed and close fuel return valves. Turn ignition on. Bleed air from fuel system. Using scan tool, command fuel pump on and wait for pressure to build. If fuel pressure is constant at 52-59 psi (3.7-4.1 kg/cm 2 ), go to step 19 . If fuel pressure is not as specified, go to next step.
  8. Using scan tool, command fuel pump on. With fuel pump running, close fuel feed valve. If fuel pressure is constant, go to step 17 . If fuel pressure is not constant, diagnose fuel injectors. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  9. If fuel pressure is suspected of dropping off during acceleration, cruise or hard cornering, go to next step. If fuel pressure is not suspected of dropping off during acceleration, cruise or hard cornering, go to step 12 .
  10. Check in-line fuel filter and fuel feed pipe for restriction. Repair as necessary. After repairs, go to step 21 . If no problem is found, go to next step.
  11. Remove fuel sending unit assembly. Check pump strainer for restriction or incorrect installation. Check for leaking fuel pump flex pipe. Ensure fuel pump is correct for vehicle application. Repair as necessary. After repairs, go to step 21 . If no problem is found, go to step 17 .
  12. Start engine and allow it to reach normal operating temperature. Observe fuel pressure gauge. If fuel pressure decreases 3-10 psi (.2-.7 kg/cm 2 ), check for intermittent problem. See «INTERMITTENTS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__intermittents) in TROUBLE SHOOTING - NO CODES - TRUCKS article. If fuel pressure does not decrease 3-10 psi (.2-.7 kg/cm 2 ), go to next step.
  13. With engine idling, disconnect vacuum hose from fuel pressure regulator. Apply vacuum (12 in. Hg) to fuel pressure regulator. If fuel pressure decreases 3-10 psi (.2-.7 kg/cm 2 ), go to step 18 . If fuel pressure does not decrease 3-10 psi (.2-.7 kg/cm 2 ), go to step 19 .
  14. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Disconnect fuel return pipe. Connect flexible fuel hose to fuel rail return outlet. Place open end of hose into container. Using scan tool, command fuel pump on. Observe fuel pressure gauge. If fuel pressure is 52-59 psi (3.7-4.1 kg/cm 2 ), go to step 20 . If fuel pressure is not as specified, go to next step.
  15. Check fuel rail outlet for restriction. Repair as necessary. After repairs, go to step 21 . If no restriction is found, go to step 19 .
  16. Check for clogged in-line fuel filter or fuel pump strainer, restricted fuel feed pipe or leaks in fuel pump flex pipe. Repair as necessary. After repairs, go to step 21 . If no problem is found, diagnose fuel pump electrical circuit. See appropriate diagnostic procedure under «NO-START DIAGNOSIS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__no-start-diagnosis) .
  17. Replace fuel sending unit assembly. After repairs, go to step 21 .
  18. Locate and repair loss of vacuum to fuel pressure regulator. After repairs, go to step 21 .
  19. Replace fuel pressure regulator. After repairs, go to step 21 .
  20. Repair restriction in fuel return pipe. After repairs, go to next step.
  21. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Reconnect all fuel system components, leaving fuel pressure gauge installed. Turn ignition on. Using scan tool, command fuel pump on. Monitor fuel pressure with fuel pump running. If fuel pressure is constant at 52-59 psi (3.7-4.1 kg/cm 2 ), system is okay. If fuel pressure is not as specified, go to step 2 .

System Description

When you turn ON the ignition switch, control module enables fuel pump, relay which powers fuel pump ON. Fuel pump remains ON as long as engine is cranking or running and control module receives ignition reference pulses. If there are no ignition reference pulses, control module shuts fuel pump OFF within 2 seconds after ignition was switched to ON position or if engine stops. Fuel tank stores fuel supply. Electric fuel pump supplies fuel through an in-line fuel filter to fuel injection system. Pump provides fuel at a higher rate of flow than is needed by fuel injection system. Fuel pressure regulator maintains correct fuel pressure to fuel injection system. A separate pipe returns unused fuel to fuel tank.

The numbers below refer to step numbers in diagnostic procedure.

  1. 2 This step verifies fuel pump is operating.
  2. 4 This step tests for an internal fuel leak. If fuel pressure decreases during this test, then an internal loss of pressure is indicated.
  3. 7 This step inspects fuel pressure regulator for a fuel leak from atmospheric vent. If fuel leaks from fuel pressure regulator while fuel pump is commanded ON, replace fuel pressure regulator.
  4. 8 This step tests for a loss of fuel pressure between shut-off adapter on fuel feed pipe and fuel pump.
  5. 9 This step tests for a leaking fuel injector or fuel pressure regulator. If fuel pressure remains constant during this test, fuel injectors are not leaking fuel.
  6. 12 This step tests for a restricted fuel return pipe. If fuel pressure is within specified values, a restriction in fuel return pipe is indicated.
  7. 14 This step determines if fuel pressure regulator, or fuel pump, is cause of low fuel pressure. If pressure rises above specified value, fuel pump is okay.
  8. 16 This step verifies that a circuit condition is not cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.
  1. Did you perform a Diagnostic System Check-Engine Controls? If yes, go to next step. If no, perform «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-132531-S16910731432002012100000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article.
  2. Turn ON the ignition, with the engine OFF. Command fuel pump ON with scan tool. Does fuel pump operate? If yes, go to next step. If no, go to «FUEL PUMP RELAY (ALL EXCEPT 2.2L & 3.0L VUE, 3.4L, 5.0L & 5.7L)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-system-component-testing__fuel-pump-relay-all-except-22l) under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  3. Turn OFF the ignition. Turn OFF all accessories. Install fuel pressure gauge. Turn ON the ignition, with the engine OFF. Command fuel pump ON with scan tool. Observe fuel pressure gauge, with fuel pump commanded ON. Is fuel pressure within 48-54 psi (334-375 kPa)? If yes, go to next step. If no, go to step 10 .
  4. Monitor fuel pressure gauge for one minute. Does fuel pressure decrease by more than 5 psi (34 kPa)? If yes, go to step 7 . If no, go to next step.
  5. Relieve fuel pressure to 10 psi (69 kPa). Monitor fuel pressure gauge for 5 minutes. Does fuel pressure decrease by more than 2 psi (14 kPa)? If yes, go to step 21 . If no, go to next step.
  6. Operate vehicle within conditions of customer's concern. Monitor fuel related parameters with scan tool. Do scan tool parameters indicate a lean condition? If yes, go to step 15 . If no, go to «SYMPTOM DIAGNOSIS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__symptom-diagnosis) under SYMPTOMS (GASOLINE) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  7. Turn OFF the ignition. Remove vent hose from fuel pressure regulator. Turn ON the ignition, with the engine OFF. Command fuel pump ON with scan tool. Inspect for a fuel leak from fuel pressure regulator atmospheric vent. Is fuel pressure regulator leaking fuel? If yes, go to step 20 . If no, go to next step.
  8. Turn OFF the ignition. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Disconnect fuel feed hose and fuel return hose from fuel rail pipes. See «FUEL LINE DISCONNECT FITTINGS»(ref-149799-S04525470992002102500000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL & TRAILBLAZER. Install (J 37287) Fuel Line Shut-Off Adapters between fuel hoses and fuel rail pipes. Open valves on fuel pipe shut-off adapters. Turn ON the ignition, with the engine OFF. Command fuel pump ON with scan tool. Bleed air from fuel pressure gauge. Command fuel pump ON and then OFF with scan tool. Close fuel feed pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to next step. If no, go to step 17 .
  9. Turn OFF the ignition. Open fuel feed pipe shut-off valve. Turn ON the ignition, with the engine OFF. Command fuel pump ON and then OFF with scan tool. Close fuel return pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to step 20 . If no, go to step 18 .
  10. Is fuel pressure more than 54 psi (375 kPa)? If yes, go to step 12 . If no, go to next step.
  11. Is fuel pressure more than 0 psi (0 kPa)? If yes, go to step 14 . If no, go to step 15 .
  12. Turn OFF the ignition. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Disconnect fuel feed hose and fuel return hose from fuel rail pipes. See «FUEL LINE DISCONNECT FITTINGS»(ref-149799-S04525470992002102500000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL & TRAILBLAZER. Attach a length of flexible fuel hose to fuel rail return pipe. Place open end of flexible fuel hose into an approved gasoline container. Turn ON the ignition, with the engine OFF. Monitor fuel pressure gauge while fuel pump is operating. Is fuel pressure within 48-54 psi (334-375 kPa)? If yes, go to step 19 . If no, go to next step.
  13. Inspect fuel rail return pipe and fuel rail outlet passage for a restriction. Did you find and correct the condition? If yes, go to step 22 . If no, go to step 20 .
  14. Turn OFF the ignition. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Disconnect fuel feed hose and fuel return hose from fuel rail pipes. See «FUEL LINE DISCONNECT FITTINGS»(ref-149799-S04525470992002102500000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL & TRAILBLAZER. Install (J 37287) between fuel return pipe and fuel rail. Open valve in fuel pipe shut-off adapter. CAUTION: DO NOT allow fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage fuel system. Turn ON the ignition, with the engine OFF. Command fuel pump ON with scan tool. Bleed air from fuel system. Monitor fuel pressure gauge. Slowly close valve in fuel return pipe shut-off adapter. Command fuel pump ON with scan tool. Does fuel pressure rise above 54 psi (375 kPa)? if yes, go to step 20 . If no, go to next step.
  15. Inspect fuel filter and fuel feed pipe for a restriction. Did you find and correct the condition? If yes, go to step 22 . If no, go to next step.
  16. Inspect harness connectors and ground circuits of fuel pump for poor connections. Did you find and correct the condition? If yes, go to step 22 . If no, go to next step.
  17. Remove fuel sender assembly. Inspect fuel pump flex hose for damage, in-tank fuel pump harness connectors for poor connections, fuel strainer for a restriction and for contaminates in fuel tank. Did you find and correct the condition? If yes, go to step 22 . If no, go to step 21
  18. Turn OFF the ignition. Raise fuel rail, with fuel pipes connected. Turn ON the ignition, with the engine OFF. Command fuel pump ON with scan tool. Locate and replace leaking fuel injector. After repairs, go to step 22 .
  19. Locate and repair restricted fuel return pipe. After repairs, go to step 22 .
  20. Replace fuel pressure regulator. After repairs, go to step 22 .
  21. Replace fuel pump. After repairs, go to next step.
  22. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to step 3 .

When you turn ON the ignition switch, the Powertrain Control Module (PCM) energizes the fuel pump relay which powers the fuel pump ON. The pump remains ON as long as the engine is cranking or running and the PCM receives reference pulses. If there are no reference pulses, the PCM shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops. An electric fuel pump pumps the fuel through an in-line filter to the fuel meter body assembly. The pump attaches to the fuel sender assembly inside of the fuel tank. The fuel pump provides fuel pressure above what is needed by the fuel injectors. The pressure regulator keeps the fuel available to the injectors at a regulated pressure. Unused fuel returns to the fuel tank by the fuel return pipe.

The number below refers to the step number in the diagnostic test.

  1. 2) This step verifies that the fuel pump is operating.
  2. 4) This step tests for an internal fuel leak. If the fuel pressure decreases during this test, an internal loss of pressure is indicated.
  3. 6) This step tests the fuel pressure regulator. The fuel pressure regulator is controlled by engine vacuum. With engine vacuum applied, the pressure should decrease by the specified value.
  4. 8) This step tests for a loss of fuel pressure between the shut-off adaptor on the fuel feed pipe and the fuel pump.
  5. 9) This step tests for a leaking fuel injector or a leaking fuel pressure regulator. If the fuel pressure remains constant during this test, the fuel injectors are not leaking fuel.
  6. 12) This step tests for a restricted fuel return pipe. If the fuel pressure is within the specified values, a restriction in the fuel return pipe is indicated.
  7. 14) This step determines if the fuel pressure regulator or the fuel pump is the cause of the low fuel pressure. If the pressure rises above the specified value, the fuel pump is okay.
  8. 16) This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all of the fuel pump electrical circuits thoroughly.
  9. 18) This step inspects the fuel pressure regulator for a fuel leak from the vacuum port. If fuel leaks from the fuel pressure regulator while the fuel pump is commanded ON, replace the fuel pressure regulator.
  1. Did you perform a Diagnostic System Check-Engine Controls? If yes, go to next step. If no, perform DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in «SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP»(ref-137937) or «SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO»(ref-132892) article.
  2. Inspect the fuel system for damage or external leaks before proceeding with this diagnostic. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Does the fuel pump operate? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  3. Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gauge. Turn ON the ignition, with the engine OFF. It may be necessary to command the fuel pump ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump ON with a scan tool. Observe the fuel pressure gauge, with the fuel pump commanded ON. Is the fuel pressure 60-66 psi (415-455 kPa) for VIN W models or 55-62 psi (379-427 kPa) for VIN X models? If yes, go to next step. If no, go to step 10 . NOTE: To identify model Vehicle Identification Number (VIN), see «GENERAL MOTORS INTRODUCTION - TRUCKS»(/gmc/yukon-denali/gmt800-1999-2006/remont/application/#enginevin-breakdown) article.
  4. The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure decrease by more than 5 psi (34 kPa). If yes, go to step 8 . If no, go to next step.
  5. Relieve the fuel pressure to 10 psi (69 kPa). Monitor the fuel pressure gauge for 5 minutes. Does the fuel pressure decrease by more than 2 psi (14 kPa)? If yes, go to step 22 . If no, go to next step.
  6. Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gauge. Start the engine. Does the fuel pressure decrease by 3-10 psi (21-69 kPa) when the engine is started? If yes, go to next step. If no, go to step 21 .
  7. Operate the vehicle within the conditions of the customer's concern. Monitor the fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition? If yes, go to step 15 . If no, diagnose by symptom. See «SYMPTOMS (GASOLINE)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__symptoms-gasoline) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  8. Turn OFF the ignition. Relieve the fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel feed pipe and the rear fuel return pipe from the chassis fuel pipes. Drain any remaining fuel into an approved gasoline container. Install the fuel pipe shut-off adapters between the rear fuel pipes and the chassis fuel pipes. Open the valves on the fuel pipe shut-off adapters. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Bleed the air from the fuel pressure gauge. Command the fuel pump ON and then OFF with a scan tool. Close the fuel feed pipe shut-off valve. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure remain constant at 3-10 psi (21-69 kPa)? If yes, go to step 17 . If no, go to next step.
  9. Turn OFF the ignition. Open the fuel feed pipe shut-off valve. Turn ON the ignition, with the engine OFF. Command the fuel pump ON and then OFF with a scan tool. Close the fuel return pipe shut-off valve. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure remain constant? If yes, go to step 21 . If no, go to step 18 .
  10. Is the fuel pressure more than 66 psi (455 kPa) for VIN W models or 62 psi (427 kPa) for VIN X models? If yes, go to step 12 . If no, go to next step.
  11. Is the fuel pressure more than 0 psi (0 kPa)? If yes, go to step 14 . If no, go to step 15 .
  12. Turn OFF the ignition. Relieve the fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel return pipe from the chassis pipe. Attach a length of flexible hose to the chassis fuel pipe. Place the open end of the flexible fuel hose into an approved gasoline container. Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gauge while the fuel pump is operating. Is the fuel pressure 60-66 psi (415-455 kPa) for VIN W models or 55-62 psi (379-427 kPa) for VIN X models? If yes, go to step 20 . If no, go to next step.
  13. Inspect the fuel rail outlet passage and the fuel return chassis pipe for a restriction. Did you find and correct the condition? If yes, go to step 23 . If no, go to step 21 .
  14. Turn OFF the ignition. Relieve the fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel return pipe from the chassis pipe. Install the fuel pipe shut-off adapter between the rear fuel return pipe and the chassis fuel pipe. Open the valve in the fuel pipe shut-off adapter. Turn ON the ignition, with the engine OFF. Bleed the air from the fuel system. Monitor the fuel pressure gauge. DO NOT allow the fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage the fuel system. Slowly close the valve in the fuel return pipe shut-off adapter. Command the fuel pump ON with a scan tool. Does the fuel pressure increase to more than 66 psi (455 kPa) for VIN W models or 62 psi (427 kPa) for VIN X models? If yes, go to step 21 . If no, go to next step.
  15. Inspect the fuel filter and fuel feed pipe for restrictions. Did you find and correct the condition? If yes, go to step 23 . If no, go to next step.
  16. Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Did you find and correct the condition? If yes, go to step 23 . If no, go to next step.
  17. Remove the fuel sender assembly. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Inspect the following items: The fuel pump flex hose for damage. The in-tank fuel pump harness connectors for poor connections. The fuel strainer for a restriction. Contaminants in the fuel tank. Did you find and correct the condition? If yes, go to step 23 . If no, go to step 22 .
  18. Open the fuel return pipe shut-off valve. Remove the fuel meter body. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Install the engine compartment fuel feed and fuel return pipes to the fuel meter body. Turn ON the ignition, with the engine OFF. Inspect for a fuel leak from the fuel pressure regulator. Is the fuel pressure regulator leaking fuel? If yes, go to step 21 . If no, go to next step.
  19. Remove the fuel injector poppet nozzles from the intake manifold in order to isolate the leaking fuel injector. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.
  20. Locate and repair the restricted fuel return pipe between the chassis fuel pipe and the fuel tank. Did you complete the repair? After repair is complete, go to 23 .
  21. Inspect for a missing or damaged "O" ring seal before replacing the fuel pressure regulator. Replace the fuel pressure regulator. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repair is complete, go to 23 .
  22. Replace the fuel pump. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repair is complete, go to next step.
  23. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step 3 .

When ignition is on, Powertrain Control Module (PCM) will activate in-tank fuel pump. In-tank fuel pump will remain ON as long as engine is cranking or running and PCM is receiving ignition reference pulses. If there are no ignition reference pulses, PCM will turn in-tank fuel pump OFF 2 seconds after ignition is turned ON or 2 seconds after engine stops running. In-tank fuel pump is an electric pump attached to fuel sender assembly. Fuel pump is designed to provide fuel at a pressure above pressure needed by fuel injectors. A fuel pressure regulator, attached to fuel rail, keeps fuel available to fuel injectors at a regulated pressure. Unused fuel is returned to fuel tank by a separate fuel return pipe.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 2 This step verifies that fuel pump is operating.
  2. 4 This step tests for an internal fuel leak. If fuel pressure drops during this test, an internal loss of pressure is indicated.
  3. 6 This step tests fuel pressure regulator. Fuel pressure regulator is controlled by engine vacuum. With engine vacuum applied, pressure should drop specified value.
  4. 9 This step inspects fuel pressure regulator for a fuel leak from vacuum port. If fuel leaks from fuel pressure regulator while fuel pump is commanded ON, replace fuel pressure regulator.
  5. 10 This step tests for a loss of fuel pressure between fuel feed pipe shut-off adapter and fuel pump.
  6. 11 This step tests for a leaking fuel injector, or fuel pressure regulator. If fuel pressure remains constant during this test, fuel injectors are not leaking fuel.
  7. 14 This step tests for a restricted fuel return pipe. If fuel pressure is within specified values, a restriction in fuel return pipe is indicated.
  8. 16 This step determines if fuel pressure regulator, or fuel pump, is cause of low fuel pressure. If pressure rises above specified value, fuel pump is okay.
  9. 18 This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.
  1. Perform OBD system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in «SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C" & "K" SERIES TRUCKS»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-control-system-self-diagnostics-48l-53l-60l) or «SELF-DIAGNOSTICS - 8.1L "C", "G" & "K" SERIES TRUCKS»(ref-138305) article. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command fuel pump ON. If fuel pump operates, go to next step. If fuel pump does not operate, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  3. Turn ignition off. Ensure all accessories are off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Install Fuel Pressure Gauge (J-34730-1A). Place fuel pressure gauge bleed hose into an approved gasoline container. Turn ignition on. Using scan tool, command fuel pump ON. Bleed air from fuel pressure gauge. It may be necessary to command fuel pump ON several times to obtain highest fuel pressure possible. DO NOT start engine. Observe fuel pressure with fuel pump operating. Fuel pressure should be 55-62 psi (385-425 kPa). If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step 12 .
  4. Monitor fuel pressure for one minute after fuel pump stops operating. If fuel pressure decreases more than 5 psi (34 kPa) in one minutes, go to step 9 . If fuel pressure does not decrease more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to next step.
  5. Relieve fuel pressure until pressure is 10 psi (69 kPa). Monitor fuel pressure gauge for 5 minutes. If fuel pressure decreases more than 2 psi (14 kPa) in 5 minutes, go to step 24 . If fuel pressure decreases 2 psi (14 kPa) or less in 5 minutes, go to next step.
  6. Turn ignition off for 15 seconds. Turn ignition on, with engine off. Monitor fuel pressure gauge. Start engine. If fuel pressure decreases 3-10 psi (21-69 kPa) when engine is started, go to next step. If fuel pressure does not decrease 3-10 psi (21-69 kPa) when engine is started, go to step 8 .
  7. Operate vehicle within conditions of customer's concern. Using scan tool, monitor fuel related parameters. If any scan tool parameters indicate a lean condition, go to step 16 . If no scan tool parameters indicate a lean condition, go to «SYMPTOMS (GASOLINE)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__symptoms-gasoline) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  8. Disconnect vacuum hose from fuel pressure regulator. Monitor fuel pressure gauge. Start engine and allow it to idle. Using a hand-held vacuum pump, apply vacuum (12-14 in. Hg) to fuel pressure regulator. If fuel pressure decreases by 3-10 psi (21-69 kPa), go to step 21 . If fuel pressure does not decrease by 3-10 psi (21-69 kPa), go to step 23 .
  9. Turn ignition off. Remove vacuum hose from fuel pressure regulator. Turn ignition on, with engine off. Using scan tool, command fuel pump ON. Inspect for a fuel leak from fuel pressure regulator vacuum port. If fuel pressure regulator is leaking fuel, go to step 23 . If fuel pressure regulator is not leaking fuel, go to next step.
  10. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Disconnect fuel feed hose and fuel return hose from fuel rail pipes. Install Fuel Line Shutoff Adapters (J-37287) between fuel hoses and fuel rail pipes. Open both valves on shutoff adapters. Turn ignition on, with engine off. Using scan tool, command fuel pump ON and then OFF. Close shutoff valve at fuel feed line. Monitor fuel pressure gauge for one minute. If fuel pressure remains constant, go to step 19 . If fuel pressure does not remain constant, go to next step.
  11. Turn ignition off. Open shutoff valve at fuel feed line. Turn ignition, with engine off. Using scan tool, command fuel pump On and then OFF. Close shutoff valve at fuel return line. Monitor fuel pressure gauge for one minute. If fuel pressure remains constant, go to step 23 . If fuel pressure does not remain constant, go to step 20 .
  12. If fuel pressure is greater than 62 psi (427 kPa), go to step 14 . If fuel pressure is 62 psi (427 kPa) or less, go to next step.
  13. If fuel pressure is greater than zero psi, go to step 16 . If fuel pressure is zero psi, go to step 17
  14. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Disconnect fuel return hose from fuel rail return pipe. Attach flexible fuel hose to fuel rail outlet passage. Place other end of flexible hose into an approved gasoline container. Turn ignition on, with engine off. Monitor fuel pressure gauge while fuel pump is operating. If fuel pressure is 55-62 psi (385-425 kPa), go to step 22 . If fuel pressure is not as specified, go to next step.
  15. Inspect fuel rail return pipe and fuel rail outlet passage for restriction. Repair as necessary. After repairs, go to step 25 . If no restriction is found, go to step 23 .
  16. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) . Disconnect fuel return hose from fuel rail return pipe. Install Fuel Line Shutoff Adapters (J-37287) between fuel return pipe and fuel rail. Open valve on shutoff adapter at fuel pipe. Turn ignition on, with engine off. Using scan tool, command fuel pump ON. Bleed air from fuel system. Monitor fuel pressure gauge. Gradually close valve on shutoff adapter at fuel return pipe. Using scan tool, command fuel pump ON. If fuel pressure increases to more than 62 psi (425 kPa), go to step 23 . If fuel pressure does not increase to more than 62 psi (4.4 kg/cm 2 ), go to next step.
  17. Inspect fuel filter and fuel feed pipe for restriction. Repair as necessary. After repairs, go to step 25 . If no restriction is found, go to next step.
  18. Inspect harness connectors and ground circuits of fuel pump for poor connections. See «WIRING DIAGRAMS»(/gmc/yukon-denali/gmt800-1999-2006/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. Repair as necessary. After repairs, go to step 25 . If connectors and ground circuits are okay, go to next step.
  19. Remove fuel sending unit assembly. Inspect fuel pump flex hose for damage, in tank fuel pump harness connectors for poor connections, fuel strainer for a restriction and for contaminates in fuel tank. Repair as necessary. After repairs, go to step 25 . If no problem is found, go to step 24 .
  20. Turn ignition off. Loosen and raise fuel rail with fuel lines connected. Turn ignition on, with engine off. Using scan tool, command fuel pump ON. Locate and replace leaking fuel injector. After repairs, go to step 25 .
  21. Locate and repair loss of vacuum to fuel pressure regulator. After repairs, go to step 25 .
  22. Locate and repair restriction in fuel return line. After repairs, go to step 25 .
  23. Replace fuel pressure regulator. After repairs, go to step 25 .
  24. Replace fuel pump assembly. After repairs, go to next step.
  25. Operate system to verify repair. If condition has been corrected, system is okay. If system is not okay, repeat step 3 .

Symptom Description

When you turn ON the ignition switch, the Powertrain Control Module (PCM) energizes the fuel pump relay which powers the fuel pump ON. The pump remains ON as long as the engine is cranking or running and the PCM receives reference pulses. If there are no reference pulses, the PCM shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops. An electric fuel pump pumps the fuel through an in-line filter to the fuel meter body assembly. The pump attaches to the fuel sender assembly inside of the fuel tank. The fuel pump provides fuel pressure above what is needed by the fuel injectors. The pressure regulator keeps the fuel available to the injectors at a regulated pressure. Unused fuel returns to the fuel tank by the fuel return pipe.

The number below refers to the step number in the diagnostic test.

  1. 2) This step verifies that the fuel pump is operating.
  2. 4) This step tests for an internal fuel leak. If the fuel pressure decreases during this test, an internal loss of pressure is indicated.
  3. 6) This step tests the fuel pressure regulator. The fuel pressure regulator is controlled by engine vacuum. With engine vacuum applied, the pressure should decrease by the specified value.
  4. 8) This step tests for a loss of fuel pressure between the shut-off adaptor on the fuel feed pipe and the fuel pump.
  5. 9) This step tests for a leaking fuel injector or a leaking fuel pressure regulator. If the fuel pressure remains constant during this test, the fuel injectors are not leaking fuel.
  6. 12) This step tests for a restricted fuel return pipe. If the fuel pressure is within the specified values, a restriction in the fuel return pipe is indicated.
  7. 14) This step determines if the fuel pressure regulator or the fuel pump is the cause of the low fuel pressure. If the pressure rises above the specified value, the fuel pump is okay.
  8. 16) This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all of the fuel pump electrical circuits thoroughly.
  9. 18) This step inspects the fuel pressure regulator for a fuel leak from the vacuum port. If fuel leaks from the fuel pressure regulator while the fuel pump is commanded ON, replace the fuel pressure regulator.
  1. Did you perform a Diagnostic System Check-Engine Controls? If yes, go to next step. If no, perform DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
  2. Inspect the fuel system for damage or external leaks before proceeding with this diagnostic. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Does the fuel pump operate? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  3. Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gauge. Turn ON the ignition, with the engine OFF. It may be necessary to command the fuel pump ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump ON with a scan tool. Observe the fuel pressure gauge, with the fuel pump commanded ON. Is the fuel pressure 60-66 psi (415-455 kPa)? If yes, go to next step. If no, go to step 10 .
  4. The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure decrease by more than 5 psi (34 kPa). If yes, go to step 8 . If no, go to next step.
  5. Relieve the fuel pressure to 10 psi (69 kPa). Monitor the fuel pressure gauge for 5 minutes. Does the fuel pressure decrease by more than 2 psi (14 kPa)? If yes, go to step 22 . If no, go to next step.
  6. Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gauge. Start the engine. Does the fuel pressure decrease by 3-10 psi (21-69 kPa) when the engine is started? If yes, go to next step. If no, go to step 21 .
  7. Operate the vehicle within the conditions of the customer's concern. Monitor the fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition? If yes, go to step 15 . If no, diagnose by symptom. See «SYMPTOMS (GASOLINE)»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes__symptoms-gasoline) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  8. Turn OFF the ignition. Relieve the fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel feed pipe and the rear fuel return pipe from the chassis fuel pipes. Drain any remaining fuel into an approved gasoline container. Install the fuel pipe shut-off adapters between the rear fuel pipes and the chassis fuel pipes. Open the valves on the fuel pipe shut-off adapters. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Bleed the air from the fuel pressure gauge. Command the fuel pump ON and then OFF with a scan tool. Close the fuel feed pipe shut-off valve. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure remain constant at 3-10 psi (21-69 kPa)? If yes, go to step 17 . If no, go to next step.
  9. Turn OFF the ignition. Open the fuel feed pipe shut-off valve. Turn ON the ignition, with the engine OFF. Command the fuel pump ON and then OFF with a scan tool. Close the fuel return pipe shut-off valve. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure remain constant? If yes, go to step 21 . If no, go to step 18 .
  10. Is the fuel pressure more than 66 psi (455 kPa)? If yes, go to step 12 . If no, go to next step.
  11. Is the fuel pressure more than 0 psi (0 kPa)? If yes, go to step 14 . If no, go to step 15 .
  12. Turn OFF the ignition. Relieve the fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel return pipe from the chassis pipe. Attach a length of flexible hose to the chassis fuel pipe. Place the open end of the flexible fuel hose into an approved gasoline container. Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gauge while the fuel pump is operating. Is the fuel pressure 60-66 psi (415-455 kPa)? If yes, go to step 20 . If no, go to next step.
  13. Inspect the fuel rail outlet passage and the fuel return chassis pipe for a restriction. Did you find and correct the condition? If yes, go to step 23 . If no, go to step 21 .
  14. Turn OFF the ignition. Relieve the fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(/gmc/yukon-denali/gmt800-1999-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel return pipe from the chassis pipe. Install the fuel pipe shut-off adapter between the rear fuel return pipe and the chassis fuel pipe. Open the valve in the fuel pipe shut-off adapter. Turn ON the ignition, with the engine OFF. Bleed the air from the fuel system. Monitor the fuel pressure gauge. DO NOT allow the fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage the fuel system. Slowly close the valve in the fuel return pipe shut-off adapter. Command the fuel pump ON with a scan tool. Does the fuel pressure increase to more than 66 psi (455 kPa)? If yes, go to step 21 . If no, go to next step.
  15. Inspect the fuel filter and fuel feed pipe for restrictions. Did you find and correct the condition? If yes, go to step 23 . If no, go to next step.
  16. Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Did you find and correct the condition? If yes, go to step 23 . If no, go to next step.
  17. Remove the fuel sender assembly. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Inspect the following items: The fuel pump flex hose for damage. The in-tank fuel pump harness connectors for poor connections. The fuel strainer for a restriction. Contaminants in the fuel tank. Did you find and correct the condition? If yes, go to step 23 . If no, go to step 22 .
  18. Open the fuel return pipe shut-off valve. Remove the fuel meter body. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Install the engine compartment fuel feed and fuel return pipes to the fuel meter body. Turn ON the ignition, with the engine OFF. Inspect for a fuel leak from the fuel pressure regulator. Is the fuel pressure regulator leaking fuel? If yes, go to step 21 . If no, go to next step.
  19. Remove the fuel injector poppet nozzles from the intake manifold in order to isolate the leaking fuel injector. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.
  20. Locate and repair the restricted fuel return pipe between the chassis fuel pipe and the fuel tank. Did you complete the repair? After repair is complete, go to 23 .
  21. Inspect for a missing or damaged "O" ring seal before replacing the fuel pressure regulator. Replace the fuel pressure regulator. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repair is complete, go to 23 .
  22. Replace the fuel pump. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repair is complete, go to next step.
  23. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step 3 .

BASIC IGNITION SYSTEM CHECKS

Note. For additional ignition system and component diagnosis, see IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.

IDLE SPEED & IGNITION TIMING (GASOLINE)

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

IDLE SPEED & INJECTION PUMP TIMING (DIESEL)

Ensure idle speed and injection pump timing/TDC offset are set to specifications. For specifications and adjustment procedures, see ON-VEHICLE ADJUSTMENTS - TRUCKS - EXCEPT TRACKER article.

SUMMARY

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

See also:
• SERVICE & ADJUSTMENT SPECIFICATIONS - TRUCKS
• WIRING DIAGRAMS
• FUEL SYSTEMS (GASOLINE)
• IGNITION SYSTEMS
• INTERMITTENTS
• FUEL PUMP RELAY (ALL EXCEPT 2.2L & 3.0L VUE, 3.4L, 5.0L & 5.7L)
• ELECTRONIC IGNITION SYSTEM DIAGNOSIS (4.2L)
• FUEL INJECTOR CIRCUIT DIAGNOSIS (4.2L)
• DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS
• HARD START
• SYMPTOMS (GASOLINE)
• FUEL LEAKS INSIDE OF ENGINE (6.6L)
• FUEL LEAKS OUTSIDE OF ENGINE (6.6L)
• FUEL SYSTEM DIAGNOSIS - PICKUP (6.6L)
• FUEL SYSTEM DIAGNOSIS - CAB & CHASSIS (6.6L)
• FUEL SYSTEM DIAGNOSIS - HIGH PRESSURE SIDE
• GLOW PLUG SYSTEM DIAGNOSIS
• FUEL HEATER INOPERATIVE DIAGNOSIS (6.6L)
• IGNITION RELAY DIAGNOSIS (8.1L)
• ELECTRONIC IGNITION SYSTEM DIAGNOSIS (8.1L)
• FUEL SYSTEM (DIESEL)
• SYMPTOM DIAGNOSIS
• GENERAL MOTORS INTRODUCTION - TRUCKS
• ON-VEHICLE ADJUSTMENTS - TRUCKS - EXCEPT TRACKER
• MODEL IDENTIFICATION
• DIAGNOSTIC AIDS
• NO-START DIAGNOSIS

More articles — Engine Performance