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Knock, Knock

Last Updated: 11/28/2007

OK, maybe not to funny, but very important. I have received many questions regarding the Knock System used on the Buick V6. The system is called the Electronic Spark Control, or ESC, system by General Motors. Although I believe that the following are all true, please verify them before making any decision involving the restoration/modification of your vehicle. If you have questions about anything listed, please use the Message Board. Information sources listed at bottom.

ELECTRONIC SPARK CONTROL (ESC) - The ESC system was first used in 1978 and is what made the turbocharger practical for Buick's V6 application.. The Achilles' heel to a turbo set up is detonation, or knocking. Under boost, detonation increases and will damage the engine. Most earlier and aftermarket system uses water injection to reduce detonation. Buick engineers developed the ESC system for the TurboV6 in 1978 and it was added to the 4.1 V6 in 1981. The system uses a sensor to "listen" for knocking. When knocking is detected, the ESC retards the engine's timing to prevent it. The more knocking, the more retarding of timing, the less performance. To avoid knocking (and therefore maximize performance) use premium, high octane, fuel. The higher the octane, the greater the fuels resistance to detonation. The 1978-'79 knock sensor is located on the intake manifold and it moved to the rear of the engine block in 1980. The "TURBO CONTROL CENTER" on the fan shroud of 1978 and '79 models is the ESC.

. ESC KNOCK SENSOR - All Turbo V6 motors use a knock, or detonation, sensor. Sensor located on the rear of the block are almost impossible to even see. For TurboV6 engines, it may be necessary to remove the Turbo/Plenum assembly to change them. When installing, refer to the appropriate Service Manual for torque specifications. Improperly tightened sensors may not operate correctly. All 1978-'82 turbo and '81-'82 4.1 engines use an accelerometer, GM part number 1997463. In 1983, the sensor was changed to a piezo element, GM number 1997562. This sensor was used on many GM engines long after 1983 and is stamped DR-562. The piezo element "generates a better signal" (according to Buick) and is much cheaper. I believe the sensor have different resistance values, so interchange is not possible unless the controller is changed or modified.

Turbo and 4.1 ESC Systems
Note: While I have proof read the numbers, please confirm them before making decisions regarding your car. Also, the books are NOT always 100% correct!

Controller: Group 2.383 (Some Controller Part Numbers are for remanufactured GM parts.)
Sensor: Group 3.682

*It may be possible to swap 1982 1st and 2nd Design controllers by also swapping the short wiring harness connected to them. 1982 1st and 2nd Design controllers can be identified by the part number located on the part itself.

** 1983 controllers and sensors were used in later years and on various engines. Check Parts Book

***On the '82 Regal the controller is found by removing the lower panel from under the steering column and looking up towards the center of the Dash board. On the '82 LeSabre, the controller is connected to the kick panel under the glove box. Other year cars with the controller under the dash should be in similar locations.

ESC System Diagnosis

The first basic check of the ESC is to simulate knocking and determine if the system retards the timing. With engine in park, running at about 1500 , tap the engine near the sensor with a long socket extension or other suitable device. The RPM should drop, indicating the timing has been retarded. If it does, the system is operating properly. (1982 Service Manual) Even better, hook up a timing light and actually watch the timing change while you tap the engine.

ESC controllers are very hard to locate and can be expensive, and many times incorrectly blamed for an improperly operating system. If you have a spare, great, but if not, rule out everything else before spending time and money on a replacement. Before proceeding further, fill the gasoline tank with fresh, premium fuel, check the engine's initial timing and EGR valve following the proper Service Manual. The recheck the ESC with a road test under load and the above simulation.

The 1978-'82 Knock sensor (Accelerometer) should have 175-375 ohms of resistance. This can be checked by disconnecting the controller and measuring between the ground and sensor wires (blue and black?, check wiring circuits in Service Manuals) or directly across the sensor itself. (1982 Service Manual)

The 1983 Knock sensor and controller were used on a wide variety of other GM engines. A quick trip to the junk should net several replacements to swap with questionable units.

A scan tool can be used to observe the knock counts on cars with an ECM.

Many knocks cannot be heard by simply listening to the engine.

If an engine is audibly knocking, the system may either not be retarding the timing at all, or possibly overwhelmed by too much knocking. Check/Correct all other possible causes of detonation such as timing, EGR, poor gasoline, overheating and sources of false knocks (bad motor mounts, etc) before concluding that the ESC system is inoperative.

Disconnecting the sensor (or a broken sensor wire) will prevent the ESC from retarding the timing at all. I believe a shorted sensor wire will retard the timing at all times.

As of May, 2000 the accelerometer sensor was still available from GM and local parts stores (Pep Boys). This may not be the case for long!

TURBO CONTROL CENTER ESC BYPASS - While it is not recommend solution, bypassing the early style (non-ECM) Turbo Control Center can be useful for diagnosis of a faulty controller  "To run the car without the ESC connected you should jumper the green wire, pin2, to the black wire ,pin 4, on the distributor side.  This is Buick's test for a duff ESC unit.  It has been my experience that the ESC affects the ignition timing under all conditions, and driving the car with the ESC disconnected will result in gross detonation."  Thanks to Peter on the TB.com message board.

Adapting the 78/80 ESC for non-factory applications

It in common to use the Turbo V6 on non-factory set ups. Many times if the engine was originally a CCC version, computer has been disabled or removed. The ESC will not function, because it requires the ECM. The non-CCC ESC can be adapted to these engines to retain the system's protection. The 1978/80 are stand alone (in other words, but need the ECM). The ESC controller, distributor, an early style knock sensor and a little rewiring are all that is required. Here is the '78/79 wiring diagram for the ESC. (1980 is similar, but the exact wiring is a little different).

Sources:
BUICK 1976 through 1981 Chassis and Body Parts Catalog, #41
BUICK Parts and Illustration Catalog, #44W
BUICK Service Manuals, 1978-1983

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