2.
Inspect connector connection, and check terminal for poor connections, loose wires, bent, broken or corroded pins, and then verify that the connectors are always securely fastened.
The measured resistance at high temperature after vehicle running may be high or low. So all resistance must be measured at ambient temperature (20℃, 68℉), unless stated otherwise.
The measured resistance in except for ambient temperature (20℃, 68℉) is reference value.
Sometimes the most difficult case in troubleshooting is when a problem symptom occurs but does not occur again during testing. An example would be if a problem appears only when the vehicle is cold but has not appeared when warm. In this case, the technician should thoroughly make out a "CUSTOMER PROBLEM ANALYSIS SHEET" and recreate (simulate) the environment and condition which occurred when the vehicle was having the issue.
Clear Diagnostic Trouble Code (DTC).
Inspect connector connection, and check terminal for poor connections, loose wires, bent, broken or corroded pins, and then verify that the connectors are always securely fastened.
Slightly shake the connector and wiring harness vertically and horizontally.
Repair or replace the component that has a problem.
Verify that the problem has disappeared with the road test.
● SIMULATING VIBRATION
Sensors and Actuators
: Slightly vibrate sensors, actuators or relays with finger.
Strong vibration may break sensors, actuators or relays
Connectors and Harness
: Lightly shake the connector and wiring harness vertically and then horizontally.
● SIMULATING HEAT
Heat components suspected of causing the malfunction with a hair dryer or other heat source.
DO NOT heat components to the point where they may be damaged.
DO NOT heat the ECM directly.
● SIMULATING WATER SPRINKLING
Sprinkle water onto vehicle to simulate a rainy day or a high humidity condition.
DO NOT sprinkle water directly into the engine compartment or electronic components.
● SIMULATING ELECTRICAL LOAD
Turn on all electrical systems to simulate excessive electrical loads (Radios, fans, lights, rear window defogger, etc.).
Handling of Connector
Never pull on the wiring harness when disconnecting connectors.
When removing the connector with a lock, press or pull locking lever.
Listen for a click when locking connectors. This sound indicates that they are securely locked.
When a tester is used to check for continuity, or to measure voltage, always insert tester probe from wire harness side.
Check waterproof connector terminals from the connector side. Waterproof connectors cannot be accessed from harness side.
Use a fine wire to prevent damage to the terminal.
Do not damage the terminal when inserting the tester lead.
Checking Point for Connector
While the connector is connected:
Hold the connector, check connecting condition and locking efficiency.
When the connector is disconnected:
Check missed terminal, crimped terminal or broken core wire by slightly pulling the wire harness.
Visually check for rust, contamination, deformation and bend.
Check terminal tightening condition:
Insert a spare male terminal into a female terminal, and then check terminal tightening conditions.
Pull lightly on individual wires to ensure that each wire is secured in the terminal.
Repair Method of Connector Terminal
Clean the contact points using air gun and/or shop rag.
Never use sand paper when polishing the contact points, otherwise the contact point may be damaged.
In case of abnormal contact pressure, replace the female terminal.
Before removing the wire harness, check the wire harness position and crimping in order to restore it correctly.
Check whether the wire harness is twisted, pulled or loosened.
Check whether the temperature of the wire harness is abnormally high.
Check whether the wire harness is rotating, moving or vibrating against the sharp edge of a part.
Check the connection between the wire harness and any installed part.
If the covering of wire harness is damaged; secure, repair or replace the harness.
Procedures for Open Circuit
Continuity Check
Voltage Check
If an open circuit occurs (as seen in [FIG. 1]), it can be found by performing Step 2 (Continuity Check Method) or Step 3 (Voltage Check Method) as shown below.
Continuity Check Method
When measuring for resistance, lightly shake the wire harness above and below or from side to side.
Specification (Resistance)
1Ω or less → Normal Circuit
1㏁ or Higher → Open Circuit
Disconnect connectors (A), (C) and measure resistance between connector (A) and (C) as shown in [FIG. 2].
In [FIG.2.] the measured resistance of line 1 and 2 is higher than 1㏁ and below 1 Ω respectively. Specifically the open circuit is line 1 (Line 2 is normal). To find exact break point, check sub line of line 1 as described in next step.
Disconnect connector (B), and measure for resistance between connector (C) and (B1) and between (B2) and (A) as shown in [FIG. 3].
In this case the measured resistance between connector (C) and (B1) is higher than 1㏁ and the open circuit is between terminal 1 of connector (C) and terminal 1 of connector (B1).
Voltage Check Method
With each connector still connected, measure the voltage between the chassis ground and terminal 1 of each connectors (A), (B) and (C) as shown in [FIG. 4].
The measured voltage of each connector is 5V, 5V and 0V respectively. So the open circuit is between connector (C) and (B).
Test Method for Short to Ground Circuit
Continuity Check with Chassis Ground
If short to ground circuit occurs as shown in [FIG. 5], the broken point can be found by performing Step 2 (Continuity Check Method with Chassis Ground) as shown below.
Continuity Check Method (with Chassis Ground)
Lightly shake the wire harness above and below, or from side to side when measuring the resistance.
Specification (Resistance)
1Ω or less → Short to Ground Circuit
1MΩ or Higher → Normal Circuit
Disconnect connectors (A), (C) and measure for resistance between connector (A) and Chassis Ground as shown in [FIG. 6].
The measured resistance of line 1 and 2 in this example is below 1 Ω and higher than 1MΩ respectively. Specifically the short to ground circuit is line 1 (Line 2 is normal). To find exact broken point, check the sub line of line 1 as described in the following step.
Disconnect connector (B), and measure the resistance between connector (A) and chassis ground, and between (B1) and chassis ground as shown in [FIG. 7].
The measured resistance between connector (B1) and chassis ground is 1Ω or less. The short to ground circuit is between terminal 1 of connector (C) and terminal 1 of connector (B1).
Possible Cause | |
● Run out of fuel ● Faulty starter ● Not connected fuel feed line ● Leakage in high pressure fuel circuit ● Fuse out of order ● Drift of the rail pressure sensor ● Cam and crank signals missing simultaneously ● Low battery voltage ● Faulty immobilizer ● Fuel pressure regulator valve contaminated, stuck, jammed ● Rail pressure regulator valve contaminated, stuck, jammed ● Bad fuel quality or water ingress in fuel | ● Inversion of fuel connections (feed ＆ return) ● Faulty fuel filter ● Clogged low pressure fuel circuit ● Clogged fuel filter ● Intermittent faulty fuel line connection ● Air ingress in the low pressure fuel circuit ● Clogged return line of high pressure fuel pump ● Low compression pressure ● Leakage at the injector ● Faulty low pressure fuel pump ● Faulty high pressure fuel pump ● Injector jammed open ● ECM program error or hardware fault ● Faulty glow system |
Possible Cause | |
● Not connected fuel return line at injector ● Leakage in high pressure fuel circuit ● Fuse out of order ● Clogged air filter ● Faulty alternator or voltage regulator ● Compensation of individual injector not adapted ● No engine coolant temperature sensor signal ● No rail pressure sensor signal ● Low battery voltage ● Electric EGR control valve blocked open ● Fuel pressure regulator valve contaminated, stuck, jammed ● Rail pressure regulator valve contaminated, stuck, jammed ● Bad fuel quality or water ingress in fuel ● Inversion of fuel connections (feed ＆ return) | ● Clogged low pressure fuel circuit ● Clogged fuel filter ● Oil level too high or too low ● Sealed or damaged catalytic converter ● Intermittent faulty fuel line connection ● Air ingress in the low pressure fuel circuit ● Clogged return line of high pressure fuel pump ● Faulty glow system ● Low compression pressure ● Clogged injector return line ● Carbon deposit on the injector (sealed holes) ● Injector needle stuck (injection possible over a certain pressure) ● Gasoline in fuel ● ECM program error or hardware fault |
Possible Cause | |
● Compensation of individual injector not adapted ● No rail pressure sensor signal ● Electric EGR control valve blocked open ● Fuel pressure regulator valve contaminated, stuck, jammed ● Rail pressure regulator valve contaminated, stuck, jammed ● Clogged air filter ● Air ingress in the low pressure fuel circuit ● Bad fuel quality or water ingress in fuel | ● Clogged return line of high pressure fuel pump ● Clogged fuel filter ● Low compression pressure ● Intermittent faulty fuel line connection ● Carbon deposit on the injector (sealed holes) ● Injector needle stuck (injection possible over a certain pressure) ● Gasoline in fuel ● ECM program error or hardware fault |
Possible Cause | |
● Not connected fuel return line at injector ● Compensation of individual injector not adapted ● No rail pressure sensor signal ● Wiring harness open or poor connection ● Air ingress in the low pressure fuel circuit ● Bad fuel quality or water ingress in fuel ● Clogged fuel filter ● Clogged air filter ● Clogged injector return line ● Leakage in high pressure fuel circuit | ● Faulty glow system ● Low compression pressure ● Poor tightening of injector clamp ● Faulty high pressure fuel pump ● Injector not adapted ● Carbon deposit on the injector (sealed holes) ● Injector needle stuck (injection possible over a certain pressure) ● Injector jammed open ● Electric EGR control valve blocked open |
Possible Cause | |
● No engine coolant temperature sensor signal ● Incorrect state of the electrical pack devices ● Faulty alternator or voltage regulator ● ECM program error or hardware fault | ● Electric EGR control valve blocked open ● Faulty accelerator pedal |
Possible Cause | |
● Compensation of individual injector not adapted ● No engine coolant temperature sensor signal ● No rail pressure sensor signal ● Electric EGR control valve blocked open ● Fuel pressure regulator valve contaminated, stuck, jammed ● Rail pressure regulator valve contaminated, stuck, jammed ● Oil level too high or too low ● Bad fuel quality or water ingress in fuel ● Sealed or damaged catalytic converter | ● Clogged air filter ● Oil suction (engine racing) ● Faulty glow system ● Low compression pressure ● Poor tightening of injector clamp ● Poor injector O-ring, no O-ring or two O-ring installed ● Injector not adapted ● Carbon deposit on the injector (sealed holes) ● Injector jammed open ● Gasoline in fuel |
Possible Cause | |
● Compensation of individual injector not adapted ● Electric EGR control valve blocked open ● Electric EGR control valve blocked open ● No engine coolant temperature sensor signal ● Faulty glow system ● Low compression pressure ● Clogged injector return line ● No rail pressure sensor signal | ● Poor injector O-ring, no O-ring or two O-ring installed ● Injector not adapted ● Carbon deposit on the injector (sealed holes) ● Injector needle stuck (injection possible over a certain pressure) ● Injector jammed open ● No engine coolant temperature sensor signal |
Possible Cause | |
● Compensation of individual injector not adapted ● Intermittent faulty fuel line connection ● Clogged exhaust system ● No rail pressure sensor signal | ● Fuel pressure regulator valve contaminated, stuck, jammed ● Rail pressure regulator valve contaminated, stuck, jammed ● ECM program error or hardware fault |
Possible Cause | |
● Blocked accelerator pedal position sensor ● Electric EGR control valve blocked open ● Intermittent faulty fuel line connection | ● Oil suction (engine racing) ● No rail pressure sensor signal ● ECM program error or hardware fault |
Possible Cause | |
● Leakage in intake system ● Incorrect state of the electrical pack devices ● Blocked accelerator pedal position sensor ● Electric EGR control valve blocked open ● Damaged turbocharger or leakage in vacuum line ● Clogged fuel filter ● Low compression pressure ● Leakage in high pressure fuel circuit | ● Fuel pressure regulator valve contaminated, stuck, jammed ● Rail pressure regulator valve contaminated, stuck, jammed ● Injector needle stuck (injection possible over a certain pressure) ● ECM program error or hardware fault |
Possible Cause | |
● Run out of fuel ● Not connected fuel feed line ● Leakage in high pressure fuel circuit ● Fuse out of order ● Bad fuel quality or water ingress in fuel ● Clogged low pressure fuel circuit ● Clogged fuel filter ● Crank signals missing ● Electric EGR control valve blocked open ● Fuel pressure regulator valve contaminated, stuck, jammed | ● Rail pressure regulator valve contaminated, stuck, jammed ● Faulty alternator or voltage regulator ● Intermittent faulty fuel line connection ● Sealed or damaged catalytic converter ● Faulty low pressure fuel pump ● Faulty high pressure fuel pump ● Gasoline in fuel ● ECM program error or hardware fault |
Possible Cause | |
● Run out of fuel ● Not connected fuel return line at injector ● Incorrect state of the electrical pack devices ● Compensation of individual injector not adapted ● Electric EGR control valve blocked open ● Faulty fuel filter ● Air ingress in the low pressure fuel circuit ● Bad fuel quality or water ingress in fuel ● Clogged fuel filter ● Intermittent faulty fuel line connection ● Wiring harness open or poor connection ● Faulty glow system | ● Low compression pressure ● Clogged injector return line ● Poor valve clearance ● Faulty low pressure fuel pump ● Poor injector O-ring, no O-ring or two O-ring installed ● Carbon deposit on the injector (sealed holes) ● Injector needle stuck (injection possible over a certain pressure) ● Injector jammed open ● Gasoline in fuel ● ECM program error or hardware fault |
Possible Cause | |
● Compensation of individual injector not adapted ● Blocked accelerator pedal position sensor ● Incorrect state of the electrical pack devices ● Electric EGR control valve blocked open ● Leakage in intake system ● Clogged air filter ● Oil level too high or too low ● Sealed or damaged catalytic converter ● Damaged turbocharger or leakage in vacuum line ● Damaged turbocharger | ● Clogged fuel filter ● Leakage at the injector ● Clogged return line of high pressure fuel pump ● Clogged injector return line ● Low compression pressure ● Injector not adapted ● Carbon deposit on the injector (sealed holes) ● Poor valve clearance ● Engine coolant temperature too high ● Fuel temperature too high |
Possible Cause | |
● Compensation of individual injector not adapted ● Oil suction (engine racing) | ● ECM program error or hardware fault |
Possible Cause | |
● Not connected fuel return line at injector ● Leakage at the Fuel pressure regulator valve ● Leakage at fuel temperature sensor ● Leakage in high pressure fuel circuit ● Leakage in intake system ● Clogged air filter ● Compensation of individual injector not adapted ● Electric EGR control valve blocked open | ● Incorrect state of the electrical pack devices ● Oil level too high or too low ● Bad fuel quality or water ingress in fuel ● Sealed or damaged catalytic converter ● Damaged turbocharger ● Low compression pressure ● Injector not adapted ● ECM program error or hardware fault |
Possible Cause | |
● Blocked accelerator pedal position sensor ● Compensation of individual injector not adapted ● Intermittent faulty fuel line connection ● Clutch not well set (optional) | ● Oil suction (engine racing) ● Damaged turbocharger ● Injector not adapted ● ECM program error or hardware fault |
Possible Cause | |
● Leakage at electric EGR control valve ● Oil suction (engine racing) ● Damaged turbocharger ● Oil level too high or too low ● Compensation of individual injector not adapted ● Sealed or damaged catalytic converter ● Poor tightening of injector clamp | ● Poor injector O-ring, no O-ring or two O-ring installed ● Injector not adapted ● Carbon deposit on the injector (sealed holes) ● Injector needle stuck (injection possible over a certain pressure) ● Injector jammed open ● ECM program error or hardware fault |
Possible Cause | |
● Compensation of individual injector not adapted ● Electric EGR control valve blocked open ● Clogged air filter ● Bad fuel quality or water ingress in fuel ● Oil level too high or too low ● Damaged turbocharger ● Sealed or damaged catalytic converter ● Oil suction (engine racing) ● Faulty air heater ● Low compression pressure ● Leakage in high pressure fuel circuit | ● Intermittent faulty fuel line connection ● Poor tightening of injector clamp ● Poor injector O-ring, no O-ring or two O-ring installed ● Injector not adapted ● Carbon deposit on the injector (sealed holes) ● Injector needle stuck (injection possible over a certain pressure) ● Injector jammed open ● Gasoline in fuel ● ECM program error or hardware fault ● Catalyzed Particulate Filter (CPF) fail |
Possible Cause | |
● Not connected fuel feed line ● Not connected fuel return line at injector ● Leakage at the Fuel pressure regulator valve | ● Leakage at fuel temperature sensor ● Leakage in high pressure fuel circuit |
Possible Cause | |
● Blocked accelerator pedal position sensor ● Incorrect state of the electrical pack devices ● Clogged air filter ● Inversion of fuel connections (feed ＆ return) ● Faulty fuel filter ● Bad fuel quality or water ingress in fuel ● Air ingress in the low pressure fuel circuit ● Clogged fuel filter ● Sealed or damaged catalytic converter | ● Intermittent faulty fuel line connection ● No rail pressure sensor signal ● Fuel pressure regulator valve contaminated, stuck, jammed ● Rail pressure regulator valve contaminated, stuck, jammed ● Gasoline in fuel ● ECM program error or hardware fault ● Faulty accelerator pedal position sensor |
Possible Cause | |
● Stuck or worn lubrication circuit of turbocharger ● Too much engine oil | ● Leakage at vacuum hose ● ECM program error or hardware fault |
Possible Cause | |
● Buzzer noise (discharge by the injectors) ● Broken clip (vibrations, resonance, noises) ● Incorrect state of the electrical pack devices ● Sealed or damaged catalytic converter | ● Leakage in intake system ● Poor tightening of injector clamp ● Damaged turbocharger ● Poor valve clearance |
