Troubleshooting procedures for ECM control system
Specifications
SUMMARY
TROUBLESHOOTING PROCEDURES FOR ECM CONTROL SYSTEM
EXPLANATION OF BASIC DIAGNOSTIC PROCEDURES
NOTE:
Perform troubleshooting according to the following diagnostic procedures. Only the basic procedures are shown here. For details, refer to the most effective procedures for each circuit as described in each system section. Before beginning troubleshooting of the corresponding circuit, check the troubleshooting procedures first.
1.
Bring in the car
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2.
Customer interview and malfunction analysis
(1) Check with the customer regarding the status and conditions when the malfunction occurred, and create an check list for interview.
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3.
Malfunction phenomenon check and diagnostic code (including freeze frame data) inspection
(1) Measure the battery voltage.
Voltage
: 11 to 14 V (engine stopped)
(2) Visually check for any blown out fuses, open or short circuit in the wiring harness, or poor contact of the connectors.
(3) Check the malfunction phenomenon and conditions, and inspect the diagnostic code according to the corresponding chart.
Diagnostic code is present.
: Refer to list of diagnostic codes.
No diagnostic code
: Refer to symptoms table.
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4.
Ascertaining vehicle conditions
(1) As some systems return to the initial conditions when parts are replaced, it is necessary to ascertain the vehicle setting conditions before repairing.
NOTE:
Setting procedures at parts removal / installation (refer to 
)
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5.
Circuit/Parts inspection
(1) Use the list of diagnostic codes or symptom table to check which system circuits and parts should be inspected.
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6.
Repair malfunction location
(1) According to Step 5, repair the system or part where the malfunction is found.
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7.
Confirmation test
(1) After repair, confirm that the malfunction no longer exists. (If the malfunction recurs, perform the confirmation test again under the same environment and conditions in which the malfunction initially occurred.)
(2) For malfunctions containing diagnostic codes, confirm the results of the diagnostic judgement.
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8.
Vehicle restoration
(1) Return all vehicle settings to the vehicle conditions checked in Step 4.
NOTE:
It is necessary to inform the customer of any locations that could not be returned to the original setting.
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Complete
MALFUNCTION ANALYSIS USING CHECK LIST FOR INTERVIEW
1. In order to identify the malfunction phenomenon correctly and make an appropriate decision, it is important not to introduce any bias into the troubleshooting process. In order to check the malfunction phenomenon, it is extremely important to ask the customer about the conditions when the malfunction occurred.
2. The following five items are valuable points in performing malfunction analysis. Sometimes, malfunction or repair history that seems not related to the current malfunction is useful. When performing troubleshooting, it is necessary to gather such information as much as possible and to correctly know how these troubles are related to the current one. Fill in each system diagnosis section of the check list for interview.
2. The following five items are valuable points in performing malfunction analysis. Sometimes, malfunction or repair history that seems not related to the current malfunction is useful. When performing troubleshooting, it is necessary to gather such information as much as possible and to correctly know how these troubles are related to the current one. Fill in each system diagnosis section of the check list for interview.
·What: Vehicle model, system name
·When: Date/Time, frequency
·Where: Route conditions
·Conditions: Driving conditions, weather
·What was happening when the malfunction occurred?: Malfunction phenomena
·When: Date/Time, frequency
·Where: Route conditions
·Conditions: Driving conditions, weather
·What was happening when the malfunction occurred?: Malfunction phenomena
NOTE:
The following is a sample check list for interview.
MALFUNCTION SYMPTOMS AND DTC CHECK
NOTE:
The diagnostic system has various functions. When a malfunction occurs in the signal circuit to the ECM, the corresponding code is stored in the ECM memory, and this is output as a diagnostic code during troubleshooting. This diagnostic function has been included so that you can freely use it to rapidly narrow down the scope of the malfunction and perform effective troubleshooting.
It is extremely important to check diagnostic codes in order to determine if the malfunction indicated by the diagnostic code is still occurring, or if the malfunction occurred in the past but now operation has returned to normal. Additionally, it is necessary to check using malfunction phenomenon inspection to determine if the malfunction indicated by the diagnostic code is directly related to the malfunction phenomenon.
For this reason, it is necessary to check the diagnostic code before and after checking the malfunction phenomenon in order to determine the current conditions. Failure to do this results in, depending on the conditions, having to perform unnecessary troubleshooting of systems that might be operating normally, making it difficult to locate the malfunction location and the performance of repairs unrelated to the malfunction. For this reason, it is necessary to always check diagnostic codes in the correct order of the procedure.
NOTE:
·The following is a flowchart that shows how to perform troubleshooting using diagnostic code checking.
·This flowchart indicates how to effectively use diagnostic code checking, and procedures for performing diagnostic code and malfunction phenomenon troubleshooting by carefully checking the results of the diagnostic code check.
·This flowchart indicates how to effectively use diagnostic code checking, and procedures for performing diagnostic code and malfunction phenomenon troubleshooting by carefully checking the results of the diagnostic code check.
1.
Malfunction identification (Interview)
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2.
DTC check
(1) Read out all DTCs.
Result
| Result |
Go to |
|---|---|
| Diagnostic code is present. |
A |
| Cannot read out from all connected ECMs. |
B |
| No diagnostic code |
C |
B
>Bus (communication lines) failure (Refer to for CAN bus failure and to LIN failure.)
for CAN bus failure and to LIN failure.)C
>Go to Step 7.
A▼
3.
Save diagnostic codes and freeze frame data
(1) Save output diagnostic codes and freeze frame data.
CAUTION:
·Do not delete before saving. Deleting these will result in the deletion of all diagnostic codes, freeze frame data and history data.
·Write down the panel diagnosis information as it cannot be saved.
·Write down the panel diagnosis information as it cannot be saved.
NOTE:
·When multiple codes are output, identify the main cause by all diagnostic codes.
·For systems in which ECM data can be checked, use input-period estimation data (data monitor).
·There are output diagnostic codes even if there is no malfunction. (Such as air conditioning sunload sensor and learning not performed after battery disconnection.)
·For systems in which ECM data can be checked, use input-period estimation data (data monitor).
·There are output diagnostic codes even if there is no malfunction. (Such as air conditioning sunload sensor and learning not performed after battery disconnection.)
Result
| Result |
Go to |
|---|---|
| Communication diagnostics and other diagnostics are present |
A |
| Other than communication diagnostics |
B |
| Communication diagnostics only |
C |
B
>Go to Step 5.
C
>Bus (communication lines) failure (Refer to for CAN bus failure and to LIN failure.)
for CAN bus failure and to LIN failure.)A▼
4.
Isolate malfunction cause
(1) From all the diagnostic codes, determine whether main cause is in parts or bus (communication line).
NOTE:
It is possible to be tailgating output of communication diagnostics due to a parts malfunction.
Result
| Result |
Go to |
|---|---|
| Part failure |
A |
| Bus (communication line) failure |
B |
B
>Bus (communication lines) failure troubleshooting (Refer to for CAN communication system and to for the large-scale multiplex communication system for vehicle body [LIN].)
for CAN communication system and to for the large-scale multiplex communication system for vehicle body [LIN].)A▼
5.
Clear diagnostic codes and freeze frame data.
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6.
Driving test, DTC check
Result
| Result |
Go to |
|---|---|
| No diagnostic code |
A |
| Diagnostic code is present. |
B |
B
>Perform troubleshooting according to the flowchart by diagnostic code.
A▼
Perform simulation test using the simulation procedures of the malfunction phenomenon.
7.
Check malfunction phenomenon
(1) Use the interview results and data monitor to determine whether the customer’s indications are malfunction.
NG
>Perform troubleshooting according to the flowchart by symptom.
OK▼
System normal
PROCEDURES FOR MALFUNCTION PHENOMENON SIMULATION
NOTE:
·The most difficult thing in troubleshooting is when there is no appearance of a malfunction phenomenon. In such cases, it is necessary to thoroughly analyze the malfunction information provided by the customer, and recreate the same conditions/environment of the customer’s vehicle that existed when the malfunction occurred. Performing troubleshooting without confirming the malfunction phenomenon results in overlooking important points of repair procedures and making mistakes such that, ultimately, troubleshooting reaches a dead end.
·For example, checking a malfunction that occurs when starting a cold engine with the engine already warmed-up, or checking for a vibration that occurs while driving on the road with the vehicle stopped limit the amount of checking and makes it impossible to identify the malfunction location.
·Although there are malfunction with causes that cannot be reproduced, such as vibration, heat or entrance of water (moisture), the procedures indicated here for malfunction phenomenon reproduction are effective means in terms of providing for external causes when a vehicle is stopped.
·For example, checking a malfunction that occurs when starting a cold engine with the engine already warmed-up, or checking for a vibration that occurs while driving on the road with the vehicle stopped limit the amount of checking and makes it impossible to identify the malfunction location.
·Although there are malfunction with causes that cannot be reproduced, such as vibration, heat or entrance of water (moisture), the procedures indicated here for malfunction phenomenon reproduction are effective means in terms of providing for external causes when a vehicle is stopped.
Important points of malfunction simulation test
Although it is necessary to check the malfunction phenomenon using malfunction phenomenon reproduction procedures, it is necessary to also find the malfunction scope/location. Doing this requires you to narrow down the circuits containing the malfunction based on the malfunction phenomenon before performing tests and connect the tester beforehand. Afterwards, perform the malfunction reproduction procedures, and determine the circuits that are faulty and those that are normal during the testing while also checking the malfunction phenomenon. Refer to the malfunction phenomenon list for each system to narrow down the cause of the malfunction phenomenon. It is also necessary to use reproduction procedures that are according to the corresponding detection conditions/time of the corresponding diagnostic code in order to reproduce diagnostic code output.
1. Vibration method: For malfunctions thought to be caused by vibration
(1) Parts and sensors
(a) Lightly tap by hand on the probable malfunctioning parts or use a similar method to vibrate them, and check if any malfunction occurs.
NOTE:
Subjecting relays to a strong impact can cause their points to open.
(2) Connectors
(a) Lightly shake the connectors up/down and right/left.
(3) Wire harnesses
(a) Lightly shake the wire harnesses up/down and left/right, and check if any malfunction occurs.
NOTE:
It is especially important to check the connector bases, vibration fulcrums and areas passing through the body.
2. Cooling/Heating method: For malfunctions thought to occur when cooled or heated
(1) Heat up or cool down (using a hair drier or coolant) the probable malfunctioning parts, and check if any malfunction occurs.
CAUTION:
·If heating: Do not heat by +60°C (can be touched by hand) or more.
·Do not heat or cool with the cover of the ECM or similar parts open so as to not directly heat or cool any electrical parts.
·Do not heat or cool with the cover of the ECM or similar parts open so as to not directly heat or cool any electrical parts.
NOTE:
Coolant can be purchased at electrical parts stores.
3. Water sprinkling method: For malfunctions thought to occur during rain or high temperature
(1) Sprinkle water on the vehicle and check if any malfunction occurs.
CAUTION:
·Do not sprinkle water directly on the engine room. Spray a fine mist of water to the front surface of the radiator to indirectly change the temperature and humidity.
·Do not sprinkle water directly on electrical parts.
·Do not sprinkle water directly on electrical parts.
4. Other: For malfunctions thought to be caused during excessive electrical load
(1) Create an excessive electrical load by operating various electrical parts such as the heater blower, headlights and rear defogger, and check if any malfunction occurs.
LIST OF DIAGNOSTIC CODES
This diagnostic codes list is for use with the diagnostic code displayed during diagnostic code checking and allows you to perform accurate and effective troubleshooting. Troubleshooting must be performed based on the inspection procedures of the diagnostic table corresponding to the displayed diagnostic code. Below is an example of the diagnostic codes list of the EFI system.
SYMPTOM TABLE
The probable malfunctioning circuit and parts corresponding to each malfunction phenomenon are shown below. This table is used for performing troubleshooting when a malfunction is still present although normal codes are displayed during DTC checking. The probable malfunction location indicates the inspection items of circuits and parts that must be checked.
NOTE:
If a malfunction is not detected by the diagnostic system although malfunction symptoms are present, it is thought that the malfunction has occurred in a location outside of the detection scope of the diagnostic system, or in a system other than the diagnostic system.
INSPECTION FLOW BY DTC SYSTEM
How to read and use each page is described below.
·Troubleshooting is shown in order of DTC, and separated by systems and symptoms in order to make it easier to diagnose malfunctions and investigate the cause.
·Troubleshooting procedures are described in sections with the following headings: “DTC”, “Circuit description”, “Detecting conditions”, “Circuit figure”, and “Inspection steps”.
·Troubleshooting procedures are described in sections with the following headings: “DTC”, “Circuit description”, “Detecting conditions”, “Circuit figure”, and “Inspection steps”.
INSPECTION PROCEDURES FOR ELECTRICAL CIRCUITS AND HOW TO PERFORM
1. Basic inspection
(1) Resistance inspection conditions for electrical parts
(a) Unless otherwise specified, all resistances are measured under an ambient temperature of 20°C. Wait until the engine has cooled after driving. If measuring right after driving a vehicle at a high ambient temperature, the resistance will not be at the specified value.
(2) Connector handling
(a) To disconnect a connector with a lock, press the connector in the joining direction until the lock tab can be easily moved and release the lock.
(b) When disconnecting a connector, hold the connector only (not pulling the harness).
(c) Before connecting a connector, check that the terminals are not deformed, damaged, missing or similarly defective.
(d) When connecting a connector with a lock, insert securely until a locking sound is heard.
(e) If checking the connector with an electrical tester, use a mini test lead and measure from the rear of the connector (harness side).
CAUTION:
·For waterproof connectors, connect directly to the sub-harness to measure as the measurement is not possible from the rear of a waterproof connector.
·Do not excessively move the inserted tester probe and be careful not to damage any terminals.
·Do not excessively move the inserted tester probe and be careful not to damage any terminals.
(3) Connector inspection procedures
(a) With the connector connected, grasp the connector housing and check the insertion status and lock effectiveness. (engagement status)
(b) With the connector separated, lightly pull on the wire harness. (missing terminals, terminal swage conditions, broken core) Visually check for presence of rust, metallic fragments, water and bent terminals. (Corrosion, foreign material, terminal deformation)
CAUTION:
If testing female gold-plated terminals, always use a male gold-plated terminal.
(c) Prepare a terminal similar to the male terminal and insert into the female terminal, and check the terminal contact pressure, engagement status and sliding weight.
(4) Connector terminal repair procedures
(a) If contacts are dirty, clean using an airgun or soft cloth. Never use sandpaper or similar material to polish the contacts as such material will cause the plating to come off if used to polish such parts.
(b) If contact pressure is not normal, replace the female terminals. At this time, use gold-plated terminals for the female terminals if the male terminals of the corresponding part are gold plated (gold color), and use tin-plated if the male terminals are tin-plated (silver color).
(c) If contacts are normal, clean contacts using an airgun or similar method and apply connector grease. (This is to prevent contact oxidation and wear.)
(5) Connector grease
(a) Connectors in locations likely to contact water such as the alternator and headlights are filled with grease (white) that prevents corrosion of terminals.
(b) Fill female terminals with connector grease if the connector grease is insufficient or terminals have been repaired.
CAUTION:
·Make sure that no dust or other foreign material is adhering.
·Do not use a screwdriver or similar tool to fill grease.
·Do not use a screwdriver or similar tool to fill grease.
(c) Although there is no problem if grease adheres to waterproof connector O-rings and rubber plugs, grease adhering to other rubber parts (such as weather stripping and grommets for wire harnesses) can result in deterioration and discoloration. If grease adheres to such parts, immediately wipe off the grease.
(6) Wire harness handling
(a) If the harness is removed, check wiring and clamp conditions before performing the procedures so that it can be securely restored.
(b) Do not twist or pull harnesses, and allow no more slack than necessary.
(c) Do not allow harnesses to be interfered with by any high-temperature locations, rotating parts, sliding parts, vibrating parts, or parts with sharp angles (such as panel edges and screw tips).
(d) Make sure that harnesses are not pinched when installing parts.
(e) Harness covering must not be damaged. If damaged, replace or repair thoroughly using vinyl tape.
2. Open circuit inspection
(1) Perform a resistance or voltage test for the open circuits of the wire harness shown in Fig. 1 to determine the location of the cause.
(2) Measure the resistance.
(a) Disconnect connectors A and C, and measure the resistance between them.
Standard value
: Less than 1 Ω
NOTE:
Measure the resistance while lightly shaking the wire harnesses up/down and left/right.
(b) For cases shown in Fig. 2, there is an open circuit between terminals 1 of connectors A and C if the resistance between terminals 1 of connectors A and C is 10 kΩ or more (open circuit), and the resistance between terminals 2 of connectors A and C is less than 1 Ω.
(c) Disconnect connector B, and measure the resistance between connectors.
(d) For cases shown in Fig. 3, there is an open circuit between terminals 1 of connectors B2 and C if the resistance between terminals 1 of connectors A and B1 is less than 1 Ω, and the resistance between terminals 1 of connectors B2 and C is 10 kΩ or more (open circuit).
(3) Measure the voltage.
(a) A voltage test is performed to check for open circuits in circuits where voltage is applied to ECM connector terminals.
(b) As shown in Fig. 4, measure the voltage for ECM 5-V output terminal in the following order with all connectors connected. Between chassis ground and terminals 1 of connector A, connector B, and then connector C.
(c) There is an open circuit in the wire harness circuit between terminals 1 of B and C if the measurement results are as follows.
Criteria
: Between terminal 1 of connector A and chassis ground: 5 V
: Between terminal 1 of connector B and chassis ground: 5 V
: Between terminal 1 of connector C and chassis ground: 0 V
3. Short circuit inspection
(1) As shown in Fig. 5, a “Ground resistance inspection” is performed if there is a short circuit of a wire harness ground to determine the location of the cause.
(2) Ground resistance inspection
(a) Disconnect connectors A and C, and measure the resistance between terminals 1 and 2 of connector A, and chassis ground.
Standard value
: 10 k Ω or more
NOTE:
Measure the resistance while lightly shaking the wire harnesses up/down and left/right.
(b) For cases shown in Fig. 6, there is a short circuit between terminals 1 of connectors A and C if the resistance is less than 1 Ω (short circuit) between terminal 1 of connector A and chassis ground, and the resistance between terminal 2 of connector A and chassis ground is 10 kΩ or more.
(c) Disconnect connector B, and measure the resistance between terminal 1 of connector A and chassis ground, and between terminal 1 of connector B2 and chassis ground. There is a short circuit between terminals 1 of connectors B2 and C if the resistance is 10 kΩ or more between terminal 1 of connector A and chassis ground, and the resistance between terminal 1 of connector B2 and chassis ground is less than 1 Ω (short circuit).
4. Visual and contact pressure inspection
(1) Disconnect the connectors on both sides.
(2) Check that there is no rust or foreign material adhering to the connector terminals.
(3) Check that rounded parts are not loose or damaged, and that the terminal is firmly secured in the lock position.
NOTE:
Make sure that the terminal does not release when slightly pulled from the rear.
(4) Insert a male test terminal into the female terminal and pull it out.
NOTE:
If it easier to pull out the test terminal in comparison with other terminals, this indicates that the contact of this part is poor.
5. ECM inspection and replacement
CAUTION:
·With the connector connected to the ECM, check from the rear of the connector on the wire harness side.
·Inspections for which no inspection conditions are indicated, perform with the engine stopped and with IG ON.
·Inspections for which no inspection conditions are indicated, perform with the engine stopped and with IG ON.
(1) First test the ECM ground circuit and repair if there is any fault. If normal, it indicates that the ECM is faulty. Replace with a normal ECM and check if there are any malfunction phenomenon present.
(a) Measure the resistance between the ECM ground terminal and chassis ground.
Standard value
: Less than 1 Ω
(b) Disconnect the ECM connector, check that there is no bending of the ground terminals on the ECM and wire harness sides, and measure the contact pressure.