Diagnosis
P0301
severe
stop driving
will fail emissions
Cylinder 1 misfire detected
One cylinder is not burning its fuel properly. Unburnt fuel goes into the exhaust and can destroy the catalytic converter in a few hundred miles, which turns a cheap repair into an expensive one.
- Vehicle
- 2018 Chevrolet Equinox LT · 1.5L Turbo · 74,905 mi
- Complaint
- shaking under acceleration, flashing light
- Scanned
- 2026-07-24 22:35
- Code family
- Powertrain · generic SAE
- Subsystem
- Ignition system or misfire
Most likely cause, given the freeze frame
Ignition coil, cylinder 1 — 31% likely
Swap the coil to another cylinder. If the misfire follows, the coil is the fault.
parts $78.00 + labour 0.4h @
$142.00/h =
$134.80
Full ranked differential
| Cause | Prior | Updated | Repair |
|---|
| Ignition coil, cylinder 1
|
34% |
31%
|
$135 |
| Spark plug, cylinder 1
|
28% |
26%
|
$85 |
| Low compression, cylinder 1
set under 78% load, mechanical causes rise
|
13% |
20%
|
$213 |
| Fuel injector, cylinder 1
|
16% |
15%
|
$344 |
| Vacuum leak local to cylinder 1
|
9% |
8%
|
$180 |
The prior column is what the code alone tells you. The updated column is after conditioning on the
freeze-frame values below. Green moved up on the evidence, red moved down.
What the diagnosis is worth
| Work the ranked path, stop when fixed |
$379 expected |
| Replace fuel injector, cylinder 1 first |
$344 |
Expected cost sums each cause's probability against the cumulative cost of reaching it in order. On this
scan the ranked path expects $379
against $344
for going straight at the expensive component, which is the quote most people are handed.
Freeze frame — sensor state when the code set
| PID | Parameter | Value |
|---|
| MAF |
Mass air flow rate |
22.8 g/s |
| RPM |
Engine RPM |
2640 rpm |
| SPEED |
Vehicle speed |
61 km/h |
| O2_B1S1 |
O2 sensor, bank 1 sensor 1 |
0.31 V |
| O2_B1S2 |
O2 sensor, bank 1 sensor 2 |
0.52 V |
| LONG_FT1 |
Long-term fuel trim, bank 1 |
6.8 % |
| SHORT_FT1 |
Short-term fuel trim, bank 1 |
4.2 % |
| ENGINE_LOAD |
Calculated engine load |
78 % |
| INTAKE_TEMP |
Intake air temperature |
34 °C |
| COOLANT_TEMP |
Engine coolant temperature |
92 °C |