P0325/27/32 Knock sensor circuit

[traka77]

Couple of days ago i got a check engine light on my 2001 GMC Yukon and so I dialed On*. And all the information they could give me is that it is the know sensor on the powertrain. Does any 1 here know of a way of fixing this issue or what I need to check? I want to thank in advanced every one for your support and hope to hear from every one.

[grampa bob]

Some info I Googled that might be of some help too you.

What does P0325 mean?
CARB (California Air Resources Board) has a consistent policy regarding monitoring knock (Ks) sensors but vehicle manufacturers don’t have a consistent way of using knock sensor circuitry. There are generally two methods that manufacturers have for using the knock sensor.
In the first design, which is found in most vehicles, the knock sensor plays an active role in controlling ignition timing. In this system, the PCM is advancing ignition timing until knock occurs and then retards timing slightly. This system runs on the verge of engine knock at all times. In this system the function of the knock sensor circuit is critical. If the sensor malfunctioned, precise ignition timing control could not be achieved.

A “dead” sensor circuit would not be able to detect actual knock, timing would be overly advanced, and NOX exhaust emissions would increase. For this reason, manufacturers that use the knock sensor in this manner are required to monitor this sensor and light the MIL light when a malfunction is detected.

In the second design, the knock sensor plays a very passive role and is really only on the engine for protection purposes. The various engine sensors send their information to the PCM to determine ignition timing. The PCM uses this information to control the ignition timing based on look-up tables stored in its memory. If ignition knock is detected, the PCM will take action and retard the timing a few degrees. This type of control is generally used to control spark knock caused by changes in fuel octane.

Used in this way, the knock sensor is less critical to emissions and may not even have a measurable emission impact. Unlike the first design, a “dead” knock sensor in this system will have little to no effect on the operation of the engine. Manufacturers that use this design are not required to monitor the sensor under EPA OBDII regulations and will not turn on the MIL if the P0325 DTC is set.

[traka77]

Well thanks grampa bob, so thats what it is. The book (chiltons) gives only the discription of the code and so thanks for the brief explanation. If i take it to the dealer do you know how much im looking to get this resolved?..



Thanks again Grampa bob.

[grampa bob]

Before taking to a dealer, Clear the code & consider filling gas tank with 91 octane. You might have just gotten some bad gas. keep it as simple as possible before spending big bucks.
You can clear the code by disconnecting the Battery if you dont' have an OBD scanner.

[traka77]

Is it like 30 minutes that the battery has to be disconnected?

[grampa bob]

Originally Posted by traka77

Is it like 30 minutes that the battery has to be disconnected?

More like ten minutes but truthfully I don.t know exactly how long battery disconnect is required but 30 minutes is usually more than enough time.

Bob