Fix P0328: Mechanic’s solutions that WORKED

The code P0328: Knock Sensor 1 Circuit High Input (Bank 1) indicates that the knock sensor on bank 1 of the engine is sending a signal that is too high. This sensor is crucial for detecting engine knock or pinging, which can cause damage to the engine. A high input signal might suggest a problem with the sensor itself, its wiring, or other engine issues causing false detections.

P0328 quick overview

Meaning	P0328: Knock Sensor 1 Circuit High Input (Bank 1)
Is it serious?	This code can be serious as it may affect engine performance and fuel efficiency, potentially leading to more significant engine issues.
Possible causes	– Faulty knock sensor – Wiring or connector issues related to the knock sensor – Engine mechanical problems causing abnormal vibrations – Issues with the Engine Control Module (ECM)
How to diagnose?	Check Knock Sensor: Inspect the knock sensor for physical damage or misplacement. Inspect Wiring and Connectors: Examine wiring and connectors for shorts, corrosion, or disconnections. Engine Inspection: Look for engine issues that could cause abnormal vibrations or noises. ECM Voltage Check: Measure voltage to/from the ECM for any abnormalities. Software Update: Consider updating the vehicle’s software or performing a hard reset.

How to fix P0328 – learn from mechanics

I looked into P0328 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Nissan

Vehicle Information: 2002 Nissan Xterra SE 3.3L – Poor Idle Quality, Hesitation, Misfire, MIL Lamp on

Issue + Repair History:

• Engine light on, flashing at times.
• Codes P0328 and P0302 consistently appearing, P0340 appeared once but did not reoccur.
• Replaced #2 spark plug, but it didn’t solve the issue.
• Vehicle lacks power and misfires under load, at idle or slow speeds.
• Compression on #2 cylinder is 135 psi, ruling out burnt valves.
• #2 injector pulsing confirmed with noid light.
• Removing plug wire from #2 cylinder doesn’t affect engine rpm or idle.

Related Repair History:

• Changed fuel and air filters (both very dirty).
• Checked all spark plug wires.
• Right valve cover replaced previously due to oil leak causing starter issues.

Other OBD2 Codes + Test Results:

• P0302: Cylinder 2 misfire.
• P0328: Knock sensor 1 circuit high output.
• P0340: Camshaft position sensor, bank 1.
• Mass air flow cleaned, readings okay.
• All grounds on manifold and cylinder head checked (previously replaced at dealer).
• O2 sensor plugs and connections okay.
• Fuel pressure at 35 psi, test okay.
• Replacing #2 plug with NGK brand made no difference.

Suggestions to Fix Issue:

• Check if #2 fuel injector is bad, including fuel trims for lean condition.
• Knock sensor likely not the main problem due to its minor effect on timing.
• Consider distributor issue, even if it doesn’t affect multiple cylinders.
• Perform a running compression test to rule out valve problems.
• Check if ignition is reaching the spark plug.
• Scope or move #2 injector for further diagnosis.
• Check operation of #2 injector (under plenum, harder to access).
• Verify the condition and operation of the distributor.
• Check for possible camshaft sensor issues.

Final Fix:

• Issue resolved by diagnosing #2 fuel injector as poor/bad.
• Replaced the #2 injector, resolving the problems.

Case #2: Nissan

Vehicle Information: 2003 Nissan Frontier XE 3.3L – MIL Lamp on

Issue + Repair History:

• Previously had trouble getting readiness test to set, with a pending P0328 (knock sensor) code.
• After setting readiness codes, the truck passed emissions.
• Codes were cleared, but MIL turned on again with two pending codes: P0328 and P0171.

Computer Codes & Descriptions:

• P0328: Pending knock sensor.
• P0171: Pending fuel trim lean.

Suggestions to Fix Issue:

• Check for air leaks in hoses, especially after the MAF sensor.
• Reset codes after checking and cleaning MAF sensor.
• Ignore knock sensor as it usually doesn’t trigger MIL on non-California emission trucks.
• Address lean code first by checking for vacuum leaks, fuel pressure, O2 sensor operation, intake leaks, and exhaust leaks.
• Consider potential MAF issues, but avoid cleaning it as it can damage a good MAF.
• Add a ground wire from the left bank cylinder head/intake manifold to the right bank head.
• Check for cracked exhaust manifold.
• Consider replacing knock sensor, especially if rusted or corroded.
• Check the A/F sensor and for vacuum leaks regarding the P0171 code.

Final Fix:

• Found and fixed a leak in one of the hoses coming off the air filter.
• Cleared the codes, and the issue was resolved.

Case #3: Audi

Vehicle Information: 2008 Audi A4 Quattro 2.0L – MIL Lamp on

Issue + Repair History:

• Lack of detailed information on testing the knock sensor.
• Seeking advice on proper testing methods for the knock sensor.

Computer Codes & Descriptions:

• P0328: Knock sensor #1 circuit high.

Suggestions to Fix Issue:

• Check for other engine management or mechanical issues causing knock sensor code, like misfires or motor mount problems.
• Inspect and clean the knock sensor connector; ensure it is torqued correctly.
• Rule out low engine oil as a common cause of the fault code.
• If knock sensor and engine misfire are the only codes, consider replacing the knock sensor.
• Use an oscilloscope to check the sensor against its counterpart.
• Assess engine performance for any skips or vibrations near the sensor.
• Read sensor data with a scanner; tap the sensor/block area to see if data changes. Jump the terminals to check for wiring resistance or sensor fault.

Final Fix:

• After an oil change and driving the vehicle for a day, the MIL turned off by itself.
• Likely that the knock sensor was detecting engine noise, which resolved on its own.
• No specific repair actions were taken beyond the oil change.

Case #4: Mazda

Vehicle Information: 2006 Mazda 6 S 3.0L – MIL Lamp on, Transmission Stuck in Limp Mode

Issue + Repair History:

• Transmission stuck in 3rd gear (limp mode).
• Check engine light on with code P0328 (knock sensor circuit high).
• Replaced knock sensor but issue persisted.
• Diagnostic findings: 3.9V at red wire and 3.6V at green wire from knock sensor in PCM connector (should be 0 volts).

Related Repair History:

• New knock sensor installed.

Computer Codes & Descriptions:

• P0328: Knock sensor circuit high.

Suggestions to Fix Issue:

• Check for wires shorted to voltage inside the harness.
• Inspect if transmission or harness was previously tampered with, possibly causing crushed wires.
• Look for common issues like neutral safety switch problems and popped fuses.
• Consider the possibility of wires pinched in the harness, causing a short.

Final Fix:

• Found wires under the brake master cylinder in the main harness were wet with brake fluid.
• The brake fluid made the wires soft, allowing trace voltage into knock sensor wires.
• Likely overflowed during brake service.
• Problem solved by running new wires past the affected area.

Case #5: BMW

Vehicle Information: 2006 BMW 525i 3.0L – MIL Lamp on

Issue + Repair History:

• Vehicle came in for state inspection with a check engine light on but no performance complaints.
• Recorded codes: P0328 and P1328, indicating high voltage (over 4.98 volts for 1-3 seconds).
• Both knock sensors were replaced, but the issue persisted.
• Voltage checks on all lines to the ECM showed normal levels (never over .525 volts).

Computer Codes & Descriptions:

• P0328: Bank 1 knock sensor high voltage.
• P1328: Bank 1 knock sensor high voltage.

Suggestions to Fix Issue:

• Perform a hard reset and full re-adaptation, followed by a full scan and reset.
• Update the DME software or perform a full CIP.
• Check if high voltage still shows in the ECM during driving, despite acceptable line voltage.
• Physically detach the Bank 1 knock sensor from the motor but keep it electrically connected to check for cold-motor knock.
• Review basics like spark plug condition, air filter status, fuel quality, and engine oil.
• Consider a defective belt tensioner on the N52 as a possible cause.
• Check the wiring and MAF sensor, and remove performance air filters if fitted.
• Ensure the DME has the latest software update.

Final Fix:

• Removed knock sensors from the block and taped them to the wire harness, which prevented codes from reappearing.
• Customer mentioned a previous hard reset and reprogramming by the dealer, but issues had returned.
• Decided to trade in the car instead of further repairs.

Advice	Description of Diagnostic Step
Check for Wiring Issues	Inspect the wiring harness for shorts, corrosion, or damage.
Consider Other Engine Issues	Rule out related engine problems that might cause knock sensor codes.
Don’t Rely Solely on Knock Sensor Code	Investigate other codes and symptoms as knock sensor codes can be misleading.
Update Software or Perform Resets	Consider updating the vehicle’s software or perform a hard reset.
Physically Inspect the Sensor	Remove and inspect the sensor itself for physical damage or misplacement.
Check Voltage to/from ECM	Measure the voltage in the lines to and from the ECM for anomalies.