Engines With Two Knock Sensors

CIS Turbo ECU Harness Connector (Pin # Locations):

There is no static test for a knock sensor, however there are ways of determining whether or not a knock sensor is working.

KNOCK SENSOR #1 (CYLS. #1 & #2)

Engine Sensor Connectors:

1. If the engine "pings" but code 2141 is NOT present, chances are the knock sensor is faulty or there is an open or shorted circuit between the sensor and the ECU. In this case there should also be a code 2142 (no signal from knock sensor). Check for open or grounded circuit between knock sensor connector terminal #2 and ECU terminal #15. Also check for open circuit between knock sensor connector terminal #1 and ECU terminal #16, &/or damaged shielding around knock sensor leads. If no wiring problems are found, replace the knock sensor.

2. If the engine pings and code 2141 is present, the knock sensor is probably OK, and there is a mechanical condition causing the noise and the code, such as excessive carbon deposits in the combustion chamber, overheating, incorrect distributor basic adjustment, or just poor quality gasoline.

NOTE: Turbo charger boost pressure is also controlled in part by the signal from the knock sensor. If the boost pressure is too great (inoperative wastegate or wastegate control), the ECU may not be able to eliminate knocking by retarding the timing. In this case, the knocking occurs mostly at high engine speeds and loads and can cause damage to pistons, rings, valves and spark plugs. If you suspect the boost pressure is too great and may be causing a knock, see also MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR in this section. If there is an overboost problem, code 2141 should be accompanied by codes 2143 and 2224. If this is the case, check wastegate for sticking or binding and see WASTEGATE FREQUENCY VALVE in this section.

3. If the engine lacks power and code 2141 is present, even though the engine may not ping, the knock sensor is probably loose or has failed, and is signaling a knock when no knock has actually occurred. This causes the ECU to retard ignition timing unnecessarily, causing a significant power loss and possibly overheating.

KNOCK SENSOR #2 (CYLS. #3, #4, AND #5)

The checks for knock sensor #2 are the same as for knock sensor #1, except that the code and one of the ECU terminals are different. Terminal #2 of knock sensor #2 is connected to ECU terminal #15. Terminals #1 and #3 of both knock sensors are connected to a common ground at ECU terminal #16.


DYNAMIC TEST

Typical Knock Sensor Signal:

The knock sensors can be tested dynamically with the use of an oscilloscope. With the ignition on, the sensors will produce a static wave pulse when a knock occurs in the cylinders associated with that sensor. The wave pattern should look similar to that shown in the diagram, and can be observed on a scope by probing terminals #1 and #2 of the sensor connectors while tapping on the engine block with a small hammer or wrench, near the sensor in question. If there is a great deal of static from the sensor, the ECU may not be able to distinguish between the static and an actual knock, and continue retarding the timing unnecessarily.