P0321: Engine speed sensor signal out of range or implausible
Ignition/distributor engine speed input range/performance
Severity: Inspect soon
P0321 means the computer sees an engine speed signal that is erratic or outside expected values, which can upset ignition timing and fuel delivery. The engine may stall or run poorly, so have it checked soon.
It gets more serious if:
- Stop: The engine stalls repeatedly or cuts out while driving. Losing engine speed information can stall the engine without warning, so avoid driving until it is checked.
P0321 in short
P0321 means the engine computer sees an unreliable signal from the engine speed (crankshaft position) sensor circuit, outside what it expects. TroubleCodes.net lists a faulty sensor, damaged wiring or connectors, and a damaged or clogged reluctor ring as the usual causes. Get it checked soon, as the engine can stall.
The computer uses the engine speed signal to time the spark and fuel. If the signal is erratic, implausible or out of range, it sets P0321.
The Delaware DMV list titles the code as the ignition/distributor engine speed input circuit range/performance, and TroubleCodes.net describes it as a crankshaft position or engine speed sensor range/performance problem.
Whether the light is on and how the engine behaves depends on the vehicle and how bad the signal is.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Defective crankshaft position / engine speed sensor
Common general cause- Why it ranks here
- TroubleCodes.net lists the sensor first among the causes.
- What would change this
- Rises if the sensor tests out of spec or the RPM signal drops out on a scan tool.
Cause 2: Damaged, corroded or loose sensor wiring or connector
Common general cause- Why it ranks here
- Burnt, shorted, disconnected or corroded wiring and connectors are listed as a cause alongside the sensor.
- What would change this
- Rises with visible damage or a signal that cuts in and out when the harness is moved.
Cause 3: Damaged or clogged reluctor ring teeth
Possible — needs testing- Why it ranks here
- Listed as a cause, but it is checked only after the sensor and wiring test good.
- What would change this
- Rises if the sensor and wiring are good and the signal is still erratic.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Inspect the sensor wiring and connector for damage, corrosion or looseness.
IfDamage or corrosion is found
It meansRepair the wiring or connector.
Points to: Damaged, corroded or loose sensor wiring or connector
IfNothing is found
It meansHave the signal tested.
Step 2: Watch engine RPM on a scan tool while cranking, and have the sensor and reluctor ring tested.
Warning:Testing near the crankshaft means working close to moving belts and hot parts, and ignition voltage is very high. Leave it to a shop.
IfThe sensor test fails or RPM drops out
It meansThe sensor is suspect.
Points to: Defective crankshaft position / engine speed sensor
IfThe signal is erratic with a good sensor and wiring
It meansHave the ring checked.
Symptoms
- Check engine light
- Hard starting or stalling Gets more serious: stop and have it checked.
- Poor performance and economy
How to fix
On your vehicle
AudiYour car
2023–2024 · RS 3
Supported by vehicle dataAudi bulletin A0123032072326_1 covers poor starting with the emission warning lamp on, engine speed sensor G28 and P0321. Whether it is still current is not verified.
2004–2008 · A4
Supported by vehicle dataAudi bulletin TSB-28-09-05 covers the engine speed sensor spacer not being required, naming P0321 among P0300, P0335, P0336 and P0322, with multiple misfires and the MIL on or flashing; Audi bulletin 28 08 04 covers the engine speed sensor spacer not being required, naming P0321 among P0300, P0335, P0336 and P0322. Whether it is still current is not verified.
2005–2008 · A6
Supported by vehicle dataAudi bulletin TSB-28-09-05 covers the engine speed sensor spacer not being required, naming P0321 among P0300, P0335, P0336 and P0322, with multiple misfires and the MIL on or flashing; Audi bulletin 28 08 04 covers the engine speed sensor spacer not being required, naming P0321 among P0300, P0335, P0336 and P0322. Whether it is still current is not verified.
A0123032072326_1Status unverified
Poor starting with emission lamp on, engine speed sensor G28, P0321
2023–2024rs-3 · issued · NHTSA 10247196
Bulletin on an engine that starts poorly with the emission warning lamp on, engine speed sensor G28, P0321. Only the NHTSA summary was read, not the bulletin itself.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
TSB-28-09-05Status unverified
MIL on, engine speed sensor spacer not required (P0300, P0335, P0336, P0321, P0322)
2004–2008a4, a6 · issued · NHTSA 10030629
Bulletin titled MIL on with engine speed sensor spacer not required, naming P0300, P0335, P0336, P0321 and P0322. The summary mentions multiple misfires and a MIL that may be on or flashing. Only the NHTSA summary was read, not the bulletin itself.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
28 08 04Status unverified
MIL on, engine speed sensor spacer not required (P0300, P0335, P0336, P0321, P0322)
2004–2008a4, a6 · issued · NHTSA 10024722
Earlier bulletin with the same title as TSB-28-09-05: MIL on, engine speed sensor spacer not required, naming P0300, P0335, P0336, P0321 and P0322. Only the NHTSA summary was read, not the bulletin itself.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
Sources and review
- P0321 trouble code
- Diagnostic Trouble Code (DTC) list
- A0123032072326_1: Poor starting with emission lamp on, engine speed sensor G28, P0321
- TSB-28-09-05: MIL on, engine speed sensor spacer not required (P0300, P0335, P0336, P0321, P0322)
- 28 08 04: MIL on, engine speed sensor spacer not required (P0300, P0335, P0336, P0321, P0322)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
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