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Engine Control System - Trouble Shooting - No Codes: Diagnosis Pontiac Vibe I

Testing & Diagnostics ~1318 words

PRELIMINARY INSPECTION

Before performing any symptom tests, perform DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 1.8L VIBE article and verify that all of the following are true before using the symptom diagnosis

  1. The Powertrain Control Module (PCM) and the Malfunction Indicator Lamp (MIL) are operating correctly.
  2. No DTCs are stored.
  3. The scan tool data is within a normal operating range.
  4. Verify customer complaint and locate the correct symptom. See «SYMPTOM DIAGNOSIS»(ref-153013-S36467972162003031100000) . Check the items indicated under that symptom.

Several of the symptom procedures call for a careful visual/physical check. DO NOT neglect to perform the visual/physical check. The visual/physical check is an important procedure that can lead to the correction of a concern without further diagnosis. The performance of the visual/physical check can save valuable time. The visual/physical check should include the following

  1. Inspect all the PCM grounds for secure and clean connections that are in the proper location.
  2. Check all vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label.
  3. Check the vacuum hoses thoroughly for any type of leak or restriction. Inspect the air inlet ducts for collapsed or restricted sections.
  4. Check for air leaks at throttle body mounting area and intake manifold sealing surfaces.
  5. Inspect the wiring harness for proper connections and damage.

SYMPTOMS - ENGINE CONTROLS

CAUTIONWhen battery is disconnected, vehicle computer may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES - GENERAL MOTORS article in GENERAL INFORMATION before disconnecting the battery.

Note. For circuit reference, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SYMPTOMS - ENGINE EXHAUST

Review the Exhaust System Description and Operation in order to familiarize yourself with the system functions. All diagnostics on a vehicle should follow a logical process. Strategy based diagnostics is a uniform approach for repairing all systems. The diagnostic flow is the place to start when repairs are necessary and may always be used in order to resolve a system problem.

Visual/Physical Inspection

  1. Inspect for aftermarket or non-OEM devices such as, but not including; tailpipe extensions, headers, and exhaust cutouts. This could affect the operation and proper performance of the exhaust system.
  2. Verify the exact operating conditions under which the concern exists. Note factors such as engine RPM, engine temperature, engine load, and frequency of concern.
  3. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause any symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

  1. Loss of power. See «RESTRICTED EXHAUST»(ref-153013-S35489441112003031100000) .
  2. Poor acceleration. See «RESTRICTED EXHAUST»(ref-153013-S35489441112003031100000) .
  3. Poor fuel economy. See «RESTRICTED EXHAUST»(ref-153013-S35489441112003031100000) .
  4. Excessive smoke - diesel. See «RESTRICTED EXHAUST»(ref-153013-S35489441112003031100000) .
  5. Exhaust hissing noise. See «EXHAUST LEAKAGE»(ref-153013-S25953431082003040300000) .
  6. Exhaust popping noise. See «EXHAUST LEAKAGE»(ref-153013-S25953431082003040300000) .
  7. Exhaust rattle noise. See «EXHAUST NOISE»(ref-153013-S18806286792003040300000) .
  8. Loud exhaust noise. See «EXHAUST NOISE»(ref-153013-S18806286792003040300000) .
  9. Exhaust buzz, groan, hum noise. See «EXHAUST NOISE»(ref-153013-S18806286792003040300000) .

Symptom Diagnosis

SymptomCheck/Repair
Misaligned Or Improperly Installed Exhaust System Components(1) Align And Tighten Components To Specification
Exhaust Leaks At Exhaust Manifold-To-Pipe, Flanges Or Pipe Clamps(1) Tighten Components To Specification
Seals Or Gaskets Leaking At Exhaust Manifold-To-Cylinder Head, Exhaust Pipes-To-Exhaust Manifold, Catalytic Converter Connection Or EGR ConnectionsReplace Leaking Seal Or Gasket
Exhaust Manifold Cracked Or Broken(2) Replace Exhaust Manifold
Exhaust System Component Connection Welds LeakingReplace Leaking Component
Muffler Or Pipe Damaged, Or Leaking At The SeamsReplace Affected Muffler Or Pipe
(1) See TORQUE SPECIFICATIONS in REMOVAL & INSTALLATION -1.8L VIBE article. (2) See appropriate article in ENGINES
(1)See TORQUE SPECIFICATIONS in REMOVAL & INSTALLATION -1.8L VIBE article.
(2)See appropriate article in ENGINES

EXHAUST LEAKAGE DIAGNOSIS

SymptomCheck/Repair
Popping Or Hissing Noise(1) Exhaust Leak.
Loud ExhaustCompare To A Known-Good Vehicle. Inspect For A Damaged Or Failed Muffler Or Pipe. Replace Faulty Muffler Or Pipe.
External Rattle Or Vibration NoiseCheck For Bent Or Loose Hanger, Loose Heat Shield, Or Loose Clamp. Check For Exhaust Pipe Causing Interference. Repair/Replace Affected Component.
Internal RattleTest Components By Tapping With A Rubber Mallet To Confirm A Rattle. Replace Faulty Catalytic Converter Or Muffler.
(1) See EXHAUST LEAKAGE .
(1)See EXHAUST LEAKAGE .

EXHAUST NOISE DIAGNOSIS

Diagnostic Procedures

  1. Verify the customers complaint. Go to next step.
  2. Did you review the exhaust symptoms diagnostic information and perform the necessary inspections? If yes, go to next step. If no, go to «SYMPTOMS - ENGINE EXHAUST»(ref-153013-S05327205772003040300000) under SYMPTOM DIAGNOSIS.
  3. Is the system equipped with dual exhaust? If yes, go to «DIAGNOSTIC AIDS»(ref-153013-S25382497802003031200000) . If no, go to next step.
  4. Remove the HO2S that is in front of and closest to the catalytic converter. Install the Exhaust Back Pressure Gauge (J 35314-A), or equivalent, in place of the HO2S sensor. Start and run the vehicle. With the engine idling at normal operating temperature, record the exhaust system back pressure reading on the gauge. Does the reading exceed 1.25 psi (8.6 kPa)? If yes, go to step 6 . If no, go to next step.
  5. With the Exhaust Back Pressure Gauge still installed, increase and monitor engine speed to 2000 RPM. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed 1.25 psi (8.6 kPa)? If yes, go to next step. If no, go to step 9 .
  6. Turn the engine off and place the ignition in the lock position. Remove the Exhaust Back Pressure Gauge. Re-install the HO2S sensor. See «HEATED OXYGEN SENSOR 1»(ref-153233-S18396672982003032600000) or «HEATED OXYGEN SENSOR 2»(ref-153233-S13470233012003032600000) under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION - 1.8L VIBE article. Remove the post-catalyst HO2S sensor. Install the Adapter (J 35314-A) in place of the post HO2S sensor. Start and idle the engine and monitor the engine speed to 2000 RPM. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed 1.25 psi (8.6 kPa)? If yes, go to next step. If no, go to step 8 .
  7. Inspect the exhaust system for damage in the exhaust pipe, debris in the exhaust pipe, muffler internal failure or 2-layer exhaust pipe separation. Repair as necessary. After repair, go to step 9 .
  8. Replace the catalytic converter. After repair, go to next step.
  9. Remove the Adapter and reinstall the HO2S sensor. Clear any codes. Road test the vehicle to verify the repair. Did you correct the condition? If yes, system is okay at this time. If no, go to step 2 .

Diagnostic Aids

For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and diagnosis should begin there.

Road Test

WARNINGRoad test vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.

The following tests should be performed with 2 people to ensure the safe operation of the vehicle.

  1. Drive vehicle while monitoring the suspect circuit with a scan tool or a DMM connected to the circuit. Look for an abnormal reading or voltage when malfunction occurs. An abnormal reading on the scan tool or an abnormal voltage on DMM display is an indication that there may be a malfunction in the circuit being monitored.
  2. If the intermittent fault sets a DTC, the diagnostic that sets the DTC can be enhanced using CHECK MODE. Operating vehicle while in check mode can enable certain DTC diagnostics to run faster. Check mode also turns some "B" type DTCs to "A" type DTCs. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 1.8L VIBE article.
  3. Certain DTCs must run before I/M system status can be determined. Any DTC that affects the status of an I/M system can be monitored indirectly on the scan tool under the I/M System Information selection. To determine which DTCs are associated with a particular I/M system test, see «INSPECTION/MAINTENANCE SYSTEM DTCS»(ref-152429-S33380700592003020400000) under DRIVE CYCLES in SELF-DIAGNOSTICS - 1.8L VIBE article. If an intermittent DTC is associated with a particular I/M system, monitoring the I/M system test can indicate whether the diagnostic for that DTC has run. When I/M system test displays a YES status, indicating system diagnostic is complete, check for applicable DTC in LAST TEST FAILED screen of the scan tool. If the DTC is not displayed, diagnostic for that DTC has run and passed, indicating that no malfunction was present this time. All DTCs MUST BE CLEARED to view CURRENT STATUS of I/M system tests. Do not forget I/M System Information tests only indicate the test has run, not if the test passed or failed. The LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.

Loss of DTC Memory

To check for proper DTC Memory function, perform the following procedure

  1. Observe the conditions for running the DTC for the Throttle Position (TP) sensor circuit low voltage DTC.
  2. Disconnect TP sensor 3-pin harness connector.
  3. Operate vehicle within Conditions for Running the DTC.
  4. MIL should illuminate upon completion of all the Conditions for Running the DTC. Two key cycles or drive trips may be required.
  5. A TP sensor circuit low voltage DTC should be stored in the PCM and remain in memory when the ignition is turned OFF.

A failure to store a DTC or failure of the DTC to remain in memory may indicate a faulty PCM.

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