Symptoms - Engine Controls
Diagnostic Instructions
Symptoms Description
Symptoms covers conditions that are not covered by DTCs. Certain
conditions can cause multiple symptoms. These conditions are listed
together under Symptoms Testing. Conditions that may only cause
specific symptoms are listed separately under Additional Symptoms
Testing. Perform the Symptoms Testing before using the Additional
Symptoms Testing.
Symptoms Definition
Cuts Out, Misses: A steady pulsation or
jerking that follows engine speed, which is usually more pronounced
as the engine load increases. This condition is not normally felt
above 1 500 RPM or 48 km/h (30 MPH). The exhaust has a steady
spitting sound at idle or at low speed. |
Hard Start: The engine cranks OK, but does not
start for a long time. The vehicle does eventually run, or may
start but immediately stall. |
Hesitation, Sag, Stumble: A momentary lack of
response as the accelerator is pushed down. This condition can
occur at any vehicle speed. This condition is usually more
pronounced when first trying to make the vehicle move, as from a
stop. This condition may cause the engine to stall in severe
conditions. |
Lack of Power, Sluggishness, or Sponginess:
The engine delivers less than expected power. Little or no increase
in vehicle speed when the accelerator pedal is pushed down part
way. |
Poor Fuel Economy: Fuel economy, as measured
by an actual road test, is noticeably lower than expected. Also,
the fuel economy is noticeably lower than it was on this vehicle at
one time, as previously shown by an actual road test. |
Rough, Unstable, or Incorrect Idle and
Stalling: The engine runs irregularly at idle. If the
engine or the vehicle may shake. Engine idle speed may vary. Either
condition may be severe enough to stall the engine. |
Surges/Chuggles: An engine power variation
under steady throttle or cruise. Feels like the vehicle speeds up
and slows down with no change in the accelerator pedal
position. |
Fuel Knock/Combustion Noise: A mild to severe
ping, usually worse under acceleration. The engine makes sharp
metallic knocks that change with the throttle opening. |
Excessive Smoke (Black): Black smoke under
load, idle or start up, hot or cold. |
Excessive Smoke (White): White smoke under
load, idle or start up, hot or cold. |
Excessive Smoke (Grey or Blue): Grey or Blue
smoke under load, idle or start up, hot or cold. |
Reference Information
Electrical Information Reference
Scan Tool Reference
Control Module References
Symptoms Verification
Verify the following conditions are true:
• |
The engine control module
(ECM) and the malfunction indicator lamp (MIL) are operating
correctly. |
• |
There are no diagnostic
trouble codes (DTCs) stored. |
• |
The scan tool data is within a
normal operating range. |
• |
The fuel system is not
leaking. |
• |
The air filter element is not
restricted. |
• |
The vehicle tires are
correctly inflated and meet original equipment
specifications. |
Symptoms Testing
Cuts Out/Misses, Hard Start, Hesitation/Sag/Stumble, Lack of
Power/Sluggishness/Sponginess, Poor Fuel Economy, Rough, Unstable,
or Incorrect Idle and Stalling, Fuel Knock/Combustion Noise,
Surges/Chuggles, or Excessive Smoke - Black, White, Gray, or
Blue
1. |
Test for the following
conditions: |
|
• |
The sensor systems for the
following: |
|
|
- |
Test for an intermittent fuel rail pressure sensor signal by
wiggling the harness between the sensor and the ECM with the
ignition ON and the engine OFF, while monitoring the parameter with
a scan tool. |
|
|
- |
Inspect for an intermittent crankshaft position sensor
signal. |
|
|
- |
Test the crankshaft position sensor for the correct resistance.
The crankshaft position sensor resistance may be out of range after
a hot soak. The resistance should be between 774-946 Ω. |
|
|
- |
Inspect the engine coolant temperature (ECT) sensor. Use the
scan tool in order to compare the ECT with the intake air
temperature (IAT) sensor on a cold engine. The ECT should be within
3°C (5°F) of the IAT. If not within the specified range,
inspect for a high resistance in the coolant sensor circuit or the
sensor. |
|
• |
The Fuel System for the
following: |
|
|
- |
Inspect for external fuel leaks. |
|
|
- |
Inspect the fuel system for a plugged fuel filter or air in the
fuel system. Refer to
Fuel System Diagnosis . |
|
|
- |
Inspect the fuel tank cap vent for proper operation. |
|
|
- |
Observe the actual desired fuel rail pressure with a scan tool,
with the engine idling. |
|
|
- |
If the ECM or a fuel injector has recently been replaced, it
may be necessary to confirm the fuel injector flow rate
values. |
|
|
- |
Inspect for restricted or plugged fuel injectors. |
|
|
- |
Inspect for a sticking Fuel Pressure Regulator. The symptom for
this condition will be an idle surge of at least 100 RPM. This
surge will be from 50 RPM above Desired Idle Speed to 50 RPM below
Desired Idle Speed. |
|
• |
Engine mechanical for the
following: |
|
|
- |
Broken or weak valve springs |
|
|
- |
Excessive oil in the combustion chamber. Leaking valve
seals |
2. |
If the above conditions do not
address the symptom, refer to the additional symptoms tests.
|
Additional Symptoms Tests
Hard Start
• |
Verify the driver is using the
correct starting procedure as described in the owners
manual. |
• |
Inspect for a restriction in
turbocharger inlet duct. |
• |
Inspect for a restriction or a
leak in the intake manifold. |
• |
Inspect for excessive
crankshaft end play that will cause the crankshaft position sensor
reluctor wheel to move out of alignment with the crankshaft
position sensor. |
Hesitation, Sag, Stumble
• |
Inspect for excessive
crankshaft end play that will cause the crankshaft position sensor
reluctor wheel to move out of alignment with the crankshaft
position sensor. |
Poor Fuel Economy
• |
Heavy loads being carried or
towed |
• |
Acceleration rate too much or
too often |
• |
Inspect the brake system for
brake drag. |
• |
Inspect the tires for the
correct air pressure. |
• |
Inspect for incorrect
operation of the speedometer. |
• |
Inspect for an air leak in the
charge air cooler. |
• |
Inspect the air conditioning
system for proper operation. |
• |
Suggest to the owner to fill
the fuel tank and inspect the fuel economy. |
• |
Suggest to the driver to read
the Important Facts on Fuel Economy in the Owner Manual.
|
Lack of Power, Hesitation, or Cut Out
• |
Compare the vehicle with a
similar module. Ensure the vehicle has an actual condition.
|
• |
Inspect for a proper
transmission operation. |
• |
Inspect the engine oil level
and quality. |
• |
Inspect for an air leak in the
charge air cooler. |
• |
Inspect for a worn or damaged
turbo charger turbine wheel, shaft or compressor wheel.
|
• |
Inspect for a restricted or
plugged exhaust. |
• |
Inspect for a restriction in
the charge air cooler. |
• |
Inspect for a skewed mass air
flow (MAF) sensor. |
• |
Inspect that the exhaust gas
recirculation (EGR) valve is fully closing. |
• |
Ensure that the EGR valve does
not bind when manually moving the valve. |
• |
Inspect the torque converter
clutch (TCC) operation. |
• |
Inspect the air conditioning
system for the correct operation. |
Rough, Unstable, or Incorrect Idle and Stalling
• |
Inspect the engine
mounts. |
• |
Inspect the intake and exhaust
manifolds for casting flash. |
• |
The exhaust system for damaged
or collapsed pipes |
• |
The exhaust manifold for a
collapsed inner wall |
• |
The mufflers for heat distress
or possible internal failure |
• |
Inspect the park neutral
position switch circuit. |
Surges/Chuggles
• |
Ensure the driver understands
the torque converter clutch (TCC) operation. |
• |
Ensure the driver understands
the A/C compressor operation. |
• |
Use the scan tool to ensure
the vehicle speed sensor (VSS) reading matches the
speedometer. |
Fuel Knock/Combustion Noise
• |
Inspect for a low engine
coolant level. |
• |
Inspect for any restricted air
flow through the radiator. |
• |
Inspect for a malfunctioning
or incorrect thermostat. |
• |
Inspect for a correct coolant
solution. The solution should be a 50/50 mix of anti-freeze and
water. |
Excessive Smoke (Black)
Normal Operation
• |
During light to moderate
acceleration there should be no black smoke. |
• |
During the 2-3 hard
accelerations after normal light load driving there may be some
black smoke momentarily but should not last for greater than 5
s. |
• |
During hard acceleration there
may always be a very faint puff of black smoke. |
Abnormal Operation
• |
Black smoke during light to
moderate acceleration |
• |
Heavy black smoke during hard
acceleration that lasts for greater than 5 s |
• |
Heavy black smoke during every
hard acceleration and/or during transmission shift
transitions |
• |
Inspect for an air leak in the
charge air cooler or the air ducts between the turbocharger and the
intake manifold. |
• |
Inspect for a restriction in
the turbocharger charge air cooler. |
• |
Inspect for a restriction in
the intake manifold. |
• |
Inspect that the EGR valve is
fully closing. Remove the EGR valve and visually inspect that there
is no light seen between the valves and the valve seats.
|
• |
Ensure that the EGR valve does
not bind when manually moving the valve. |
• |
Inspect for excessive oil
entering the combustion chamber. |
Excessive Smoke (White or Gray)
• |
Inspect the coolant level in
the reservoir. White coolant smoke may be mistaken for blue/gray
smoke. If the coolant level is low, refer to
Loss of Coolant . |
• |
If excessive smoke is present,
inspect for a stuck open fuel injector by performing the following
procedure: |
|
2.1 |
Disconnect the electrical
connector at the fuel injection pump. |
|
Note: Do not stand in front
of the glow plug holes while cranking the engine.
|
|
2.3 |
Crank the engine while
observing the glow plug holes for fuel spray. |
|
2.4 |
Replace the fuel injectors for
the cylinders that spray fuel. |
|
2.5 |
Inspect for contaminated oil
or high oil level. |
• |
If the ECM or a fuel injector
has recently been replaced, it may be necessary to confirm the fuel
injector flow rate values. |
• |
Inspect the fuel
injectors. |
|