Electronic Spark Advance Control (ESC) (for engines produced in 1990-1992) or a system with a knock sensor (KS) (for engines produced since 1993.).
Note: In 1993, the name of the Electronic Spark Plug (EST) system was changed. The system still works as before, but is now called a knock sensor (KS) system.
Engine with a working volume of 3.1 liters
General description
1. The appearance of detonation in a running engine may be caused by the different quality of fuel of different brands.
2. The Electronic Spark Control (ESC) system is designed to change the ignition timing by angles up to 20° in order to eliminate detonation in the engine. This allows the engine to use ignition timing with maximum efficiency, which improves engine performance and fuel economy.
3. If there is no detonation, the ESC system knock sensor (see illustration) sends a signal of 8-10 V to the ECM, after which the ECM ensures the normal timing advance is set. When the sensor detects an increased vibration level (when detonation occurs), the ESC unit disconnects the circuit going to the ECM control unit, and the voltage on its contact "B7" drops to zero. The ECM then sends a spark retard signal to the EST distributor until the detonation stops.
6.3. The knock sensor is located in the lower part of the engine compartment, closer to the passenger compartment
4. A faulty signal from the ESC knock sensor or a broken ground wire in the ESC unit will cause the signal voltage to the ECM to remain high. Under these conditions, the ECM will control the EST system as if there is no detonation. Therefore, the distributor will not set the ignition delay and when the engine is running under high load, the detonation level can become very high. Then the ECM will issue code 43.
5. If there is no signal from the ESC system to the ECM, the latter will continuously send a signal to the EST to set the ignition delay. As a result, the engine throttle response will slow down and the ECM will issue code 43.
Examination
6. The sequence of checking the ESC system is shown in the diagram (see diagram).
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6.6. Sequence diagram of the ESC (or KS) system test on a 3.1L engine
This scheme should only be used after checking all other possible factors contributing to the occurrence of detonation, such as the amount of ignition advance, the serviceability of the exhaust gas recirculation system (EGR), engine temperature, excessive noise during operation, etc.
Replacement of elements
ESC knock sensor
7. Disconnect the cable from the negative terminal of the battery.
8. Pull the insulating tube off the sensor and disconnect the electrical connector from it.
9. Remove the knock sensor from the cylinder block.
10. The sensor is installed in the reverse order.
ESC block
11. Disconnect the cable from the negative terminal of the battery.
12. Remove the glove box (see chapter 11, section 26).
13. Locate the unit mounted on the ECM bracket behind the glove box.
14. Disconnect the connector from the unit.
15. After unscrewing the bolts, remove the block from the car.
16. The unit is installed in the reverse order.
Engine with a working volume of 3.8 liters
General description
17. The ESC system in this engine consists of a knock sensor and a PCM unit. The MEM-CAL unit installed on the engine has the same functions as the ESC units that are equipped with other engine models. All diagnostic procedures for checking this system must be carried out at a service center or a specialized repair shop.