Damaged or corroded electrical connector at knock sensor 4; Faulty knock sensor 4 (internal failure or cracked housing); Open or shorted wiring in the knock sensor 4 circuit (signal or ground); Loose or improperly torqued knock sensor 4 mounting bolt; Engine mechanical noise (e.g., from a failing lifter or piston slap) mimicking a knock signal; Corrosion or water intrusion in the sensor connector or wiring harness; Faulty DME (rare, but possible if all other components test good)

DTC codes / BMW codes / P1332

P1332 · BMWKnock Sensor 4 Low Input

Q: What does code P1332 mean?

Knock Sensor 4 Low Input. P1332 on a BMW means the engine control module (DME) has detected an abnormally low voltage signal from knock sensor number 4, which is mounted on the engine block to listen for detonation. The DME compares this signal against expected values and flags the circuit as faulty when the input stays below the minimum threshold.

P1332 on a BMW means the engine control module (DME) has detected an abnormally low voltage signal from knock sensor number 4, which is mounted on the engine block to listen for detonation. The DME compares this signal against expected values and flags the circuit as faulty when the input stays below the minimum threshold.

SystemPowertrain

Code typeBMW specific

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine performance or power due to the DME retarding ignition timing as a protective measure
Rough running or hesitation under acceleration if the knock sensor signal is intermittent
Poor fuel economy as the engine runs with less optimal ignition timing
In rare cases, a slight knocking or pinging noise if the DME cannot properly detect detonation

Common causes, most likely first

Damaged or corroded electrical connector at knock sensor 4
Faulty knock sensor 4 (internal failure or cracked housing)
Open or shorted wiring in the knock sensor 4 circuit (signal or ground)
Loose or improperly torqued knock sensor 4 mounting bolt
Engine mechanical noise (e.g., from a failing lifter or piston slap) mimicking a knock signal
Corrosion or water intrusion in the sensor connector or wiring harness
Faulty DME (rare, but possible if all other components test good)

How to diagnose and fix it

Perform a visual inspection of knock sensor 4, its connector, and wiring for damage, corrosion, or loose mounting
Check the sensor mounting bolt torque to ensure it is within specification
Measure the resistance of knock sensor 4 and compare to BMW specifications; replace if out of range
Inspect the wiring harness for continuity and shorts between the sensor and DME; repair as needed
Clear the fault code and test-drive the vehicle to see if P1332 returns
If the code persists, swap knock sensor 4 with a known-good sensor from another cylinder to see if the fault moves
As a last resort, diagnose the DME for internal faults or software issues

Knock sensor 4 low input pitfalls

A loose knock sensor bolt is a common cause that is often overlooked because the sensor itself tests fine on the bench.
Engine mechanical noises such as a failing timing chain tensioner can create vibrations that the DME interprets as a low knock signal, leading to misdiagnosis.
The knock sensor circuit is sensitive to resistance changes; even a slightly corroded connector can cause P1332 without visible damage.
On some BMW engines, the knock sensors are located under the intake manifold, making access difficult and increasing the chance of harness damage during other repairs.
P1332 specifically refers to sensor 4; always verify the sensor numbering and location for the particular engine before ordering parts.

Can I keep driving with P1332?

You can generally drive the vehicle with P1332, but avoid heavy acceleration or towing until the fault is repaired, as the engine may be running with reduced ignition timing and performance. Prolonged driving with a faulty knock sensor can lead to engine damage if detonation goes undetected.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.