SELF-DIAGNOSTIC SYSTEM
Note. When diagnosing vehicle, read faults before starting diagnostic work. During some testing procedures, components are disconnected with engine running causing simulated faults. Ensure faults are recorded before starting diagnostic work to ensure only actual faults are diagnosed.
Performance/Speedometer Test
Disconnecting Electronic Stability Program (ESP), Acceleration Slip Regulation (ASR), Electronic Traction Stability (ETS), Anti-lock Brake System (ABS) control modules is not allowed. The Engine Control Module (ECM) and Transmission Control Module (TCM) rely on these modules for Vehicle Speed Sensor (VSS) data through the Controller Area Network (CAN) bus. To disable brake and engine regulation functions of the ESP, ASR, ETS, ABS control modules, perform one of the following procedures
- Working without scan tool Turn ignition off, connect Adapter (140 589 14 63 00) to underhood Data Link Connector (DLC), jumper adapter sockets No. 1 and 6, start engine, BAS/ESP or BAS/ASR lights must illuminate. Erase DTCs after completing work.
- Using scan tool Turn ignition off, disconnect front axle Vehicle Speed Sensor (VSS) connector, ESP/ASR light must illuminate. When diagnostic/repair work is completed, reconnect VSS connector. Erase DTCs after completing work.
Using Generic Scan Tool
Turn ignition off. Connect generic scan tool to diagnostic connector located under left side of dashboard. (Scheme 9) Turn ignition on. Follow tool manufacturer's instructions for reading fault codes. If no fault codes are present, but vehicle is experiencing a problem, go to SYMPTOM DIAGNOSTICS.
Scheme 9
HOW TO READ DIAGNOSTIC INFORMATION
Diagnostic information is located in 6 different categories: FUEL INJECTION SYSTEM TESTS, IGNITION SYSTEM TESTS, ELECTRONIC ACCELERATOR TESTS, CRUISE CONTROL TESTS, FUEL INJECTOR TESTS and FUEL PUMP TESTS. The far left column in testing format in all categories is a numerical step. For reading and understanding fault code diagnosis, as an example, using FUEL INJECTION SYSTEM TESTS, start at step 1.2. Under TEST SCOPE column, component or circuit being tested is voltage supply (circuit 30). Under TEST CONNECTION column, using DVOM, measure voltage between socket box terminal No. 1 and socket box terminal No. 12. Measurement is being made between Data Link Connector (DLC - X11/4) terminal No. 1 and Engine Control Module (ECM) connector terminal No. 4 on connector "B" as identified by (4B). Manufacturer recommends using Socket Box (129 589 00 21 00) for making measurements to prevent damage to electrical connectors and terminals. (Scheme 10) Under TEST CONDITION column, make measurement with ignition on. Voltage is 11-14 volts under NOMINAL VALUE column. If voltage is not within specification, follow instructions under POSSIBLE CAUSE/REMEDY column. Repair or replace wiring as necessary at relay module (K40) on SLK230 (model 170) or passenger-side fuse/relay panel module box (K40/4) on C230 (model 202). Manufacturer identifies all system components with an alphanumeric identification in testing procedures (i.e., N3/10 is for ECM). See COMPONENT/CIRCUIT IDENTIFICATION.
Note. When connecting test equipment, disconnect Engine Control Module (ECM) connector "D" first. When reconnecting connectors, connect connector "D" last. See ECM CONNECTOR IDENTIFICATION .
Scheme 10
SYMPTOM DIAGNOSTICS
For symptom diagnosis chart reference, refer to the following list.
- Engine starts and accelerates poorly when cold. (Scheme 11)
- Engine does not start. (Scheme 11)
- Engine has uneven idle. (Scheme 11)
- Engine has insufficient output. (Scheme 12)
- Engine runs unevenly (shakes). (Scheme 12)
- Engine runs unevenly (misfiring). (Scheme 12)
- Engine surges after cold start. (Scheme 12)
- Transmission failure during warm-up. (Scheme 13)
- Transmission failure when warm or increased fuel consumption. (Scheme 13)
- Engine vibrates. (Scheme 13)
- EA is in "limp home" mode. (Scheme 13)
