C4, C5 Corvette OBD-II LT1/LT4 Knock Sensor

1996, 1997

This part is a new C4 to C5 OBD-II LT1/LT4 Knock Sensor which can be installed on any of the following Corvette models:

Year	Body & Trim
1997	Base
1996	Base, Collector’s Edition, Grand Sport

 

What is a knock sensor?

The knock sensor system is used for the detection of detonation. The computer retards advance based on the amount of knock received. The knock sensor produces an ac voltage according to the amount of knock. The computer receives the signal and its programming determines how the computer will change the spark advance.

Diagnostic Trouble Code 43 (OBD-I) or P0332 (OBD-II) can result from a knock sensor circuit or sensor that is faulty. When the DTC is present, the computer will automatically retard timing to protect the engine (since it can no longer sense potentially destructive detonation). Timing can be retarded 10° or more in some driving situations. Performance will be affected.

The sensor resides on the RH side (passenger) of the engine block, in the coolant drain location. The F-body uses only one sensor. Other body platforms may use two sensors on their LT1 applications.

On the 1994-1997 LT1 F-body PCM, there is a replaceable module that receives the knock signal. 1993 ECM’s have the receiver circuitry built-in to the computer and have no replaceable module.

You may have heard about an LT4 knock module. This module came from the 1996 LT4 Corvette, that had roller rockers as standard equipment. The LT4 module is tuned to allow for the noise the rockers make (not perceiving it as knock). If you have similar valve train modifications on your LT1, it may be a good idea to swap to the LT4 module to reduce the chance of “false knock” (knock not related to detonation).

The LT4 module can be used on 1994 to 1997 engines (OBD-I and II) and no change of the knock sensor is needed (even though the sensors changed in 1996). There is no specific LT4 knock sensor. However, there are differences in the impedance of the sensors between OBD-I and II as listed in the testing section below. You must use the sensor that is matched to your OBD type (or have a wiring modification as frequently done in an OBD type swap situation).

 

Testing for OBD-1 vs. OBD-II Knock Sensor

1. With the connector off the knock sensor, check for 5V on the harness terminal with the key turned to the ON position. Continue if that is good. If not good, check at pin C8 (1993), D22 (1994 to 1997) on the back of the computer. If the voltage is ok at the back of the computer, repair the wire from the computer to the sensor.
2. Turn the key to the OFF position. With the connector off at the knock sensor, measure the resistance between the knock sensor terminal and the ground. The resistance should be between 3300 to 4500 ohms (OBD-I) or 93k to 107k ohms (OBD-II). If it is not, the sensor is faulty or the sensor is not making good contact with the block. Try another resistance reading from the sensor terminal to the outside metal of the sensor body.
3. If all that is good, it might be a faulty knock module (in the case of 1994 to 1997) or a problem with the computer, itself.

Knock sensor operation can be monitored with a scanner. Rapping on the RH exhaust manifold or engine block with a hammer should cause the scanner knock value to increment.

 

GM Part Number: 10456287

ACDelco Part Number: 213-325

Weight	0.10 lbs
Dimensions	2.60 × 2.00 × 1.60 in
Generation	C4 (1984-1996), C5 (1997-2004)
Year	1996 ('96), 1997 ('97)
Body Type	Convertible (1YY67), Coupe (1YY07)
Product Condition	New (GM)
Manufacturer	ACDelco