P1375

Insufficient RMP Increase During Spark Test

Powertrain Ignition System Spark Advance Test Failure 🟡 Moderate — Fix within a week ⚠️ Drive with Care
💬

What This Actually Means

In plain language — no jargon

During a spark test, your engine's RPM didn't increase as expected, like trying to rev an engine with the choke stuck on. The ECU is saying the ignition system isn't responding properly to the test signal.

⚡

Symptoms You May Notice

3 known symptoms for this code
Check Engine Light illuminated
Engine hesitation or stumbling during acceleration
Difficulty starting or rough idle
🔬

How Your ECU Detects This

Technical sensor logic and voltage thresholds

During a spark advance test, the ECU commands increased ignition timing and monitors for a corresponding RPM rise. If RPM fails to increase by the minimum threshold within the expected time window, this fault is triggered. The ECU uses crankshaft speed sensors to detect the response.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
RPM increase during spark test 100-200+ RPM rise within 1-2 seconds Less than 50 RPM rise or no detectable increase
Spark timing advance response Timing advances 5-10 degrees smoothly Timing does not advance or advances erratically
🔧

Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Spark plugs
Replace all spark plugs with OEM equivalents; worn plugs prevent proper ignition response.
2
Ignition coil(s) or spark plug wires
Test and replace any failed coil packs or corroded/cracked plug wires affecting spark delivery.
3
CKP (Crankshaft Position) sensor
Clean or replace if ECU cannot accurately read engine speed changes; sensor contamination is common.
⚠️

When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code P1375 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
🔄

How to Clear Code P1375

What happens after you fix the fault

Once the fault is repaired, P1375 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.