Symptom
The fault comes and goes
It happens, then it does not, and nothing you do reliably brings it back — the warning clears itself, or the garage cannot make it appear. This is a finding rather than a frustration, and it points somewhere specific. A part that has failed stays failed; a fault that comes and goes is usually a connection that is only sometimes a connection — a corroded pin, a chafed wire touching a bracket, a joint that opens as things warm and expand. That is why the codes for these end in Intermittent rather than High or Low. Write down what the car was doing each time it happened; the pattern nobody can reproduce on a ramp is often obvious across three notes.
Also described as: comes and goes, intermittent fault, happens sometimes, not every time, fault disappears, cant reproduce it, random fault, گاهی هست گاهی نیست, ایراد مقطعی است, خودش خوب میشود, falla a veces, va y viene, fallo intermitente, المشكلة تروح وتجي, عطل متقطع, أحيانا تحصل وأحيانا لا
Some causes mean you should stop driving
25 of the 359 codes that produce this symptom indicate a fault where continuing to drive risks damage or is unsafe. If the symptom is sudden or severe, treat it as one of those until a scan says otherwise.
What this usually means
This is a finding rather than a frustration, and it points somewhere specific. A part that has failed stays failed. A fault that comes and goes is usually a connection that is only sometimes a connection — a corroded pin, a chafed wire touching a bracket, a joint that opens as things warm and expand. That is why the codes for these end in Intermittent rather than High or Low.
The whole difficulty is that the car is behaving perfectly when somebody looks at it, so the method is to stop waiting and start provoking. Workshop practice has four ways to do that, and each targets a different cause:
- The wiggle test. Flex the harness and connectors by hand while watching live data or a meter set to record minimum and maximum. A reading that jumps as you move one section has just named it. Some scan tools have a dedicated wiggle mode that alerts on a dropout so you can watch your hands instead of the screen.
- Heat. A heat gun on a low setting, about 15 cm away, reproduces the classic hot-soak failure — a joint that opens as metal expands, a cracked solder joint, a semiconductor that stops at temperature.
- Cold. Freeze spray chills one component at a time to around −50 °C. A fault that disappears when a specific part is chilled has been localised precisely.
- Water. A hose or spray bottle, one area at a time, for anything that only misbehaves in the wet.
Where none of that provokes it, record instead of chase. A data logger left running while the car is driven normally captures what happens at the moment it happens — and the freeze-frame data attached to the stored code is the same evidence for free, which is why clearing a code before reading its frame throws away the only record anybody was going to get.
And write down what the car was doing each time. The pattern nobody can reproduce on a ramp is often obvious across three notes.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Codes end in 'Intermittent' rather than High, Low or Open | A connection that is only sometimes a connection — corrosion, a backed-out pin, or a wire broken inside intact insulation | Wiggle-test the harness and connectors while watching live data, or a meter recording minimum and maximum. A reading that jumps as one section moves names it. | Repair the connection and secure the harness clear of what was chafing it. Renewing the component the code names usually changes nothing. |
| Appears after twenty minutes or on a long run, clears after standing | Thermal — a joint opening as metal expands, or a semiconductor failing at temperature | Heat gun on low, about 15 cm away, on one suspect area at a time while monitoring the signal. Reproducing it deliberately is faster than waiting for it. | Repair the joint or renew the component the heat test implicates. A cold bench test on this fault passes and proves nothing. |
| Present when the car is cold or in cold weather, gone once warm | The opposite thermal case — a joint that closes as it expands, or a component out of tolerance cold | Freeze spray one component at a time while monitoring. A fault that appears or clears as a specific part is chilled has been localised. | Repair or renew what the cold test names. Both thermal directions are real and they need opposite tools. |
| Follows rain, washing or damp mornings | Damp bridging two pins, or corrosion that is only a bad connection when wet | Spray one area at a time with a hose or bottle while monitoring live data. This is one of the few faults a driver can help reproduce on a driveway. | Dry, clean and seal the connector, and repair whatever route lets the water in. See the wet-weather entry in this vocabulary. |
| Nothing provokes it in a workshop | Not absent — merely not reproducible on a ramp, which is a different thing | Fit a data logger and drive the car normally until it happens, then read the log around the event. Read stored freeze-frame data before clearing anything. | Repair what the log or frame names. This is the case where the driver's written notes are worth more than any bench test. |
| Several unrelated systems affected at the same moments | Supply or earth rather than any of the named systems — modules misbehave together when voltage sags | Voltage-drop test the main earths and supply under load rather than at rest. A resting continuity check passes a joint that fails under current. | Remake the earth or repair the supply, then clear and re-scan. Only what returns is real. |
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Codes end in 'Intermittent' rather than High, Low or Open
- Likely cause
- A connection that is only sometimes a connection — corrosion, a backed-out pin, or a wire broken inside intact insulation
- How to confirm it
- Wiggle-test the harness and connectors while watching live data, or a meter recording minimum and maximum. A reading that jumps as one section moves names it.
- What fixes it
- Repair the connection and secure the harness clear of what was chafing it. Renewing the component the code names usually changes nothing.
-
Appears after twenty minutes or on a long run, clears after standing
- Likely cause
- Thermal — a joint opening as metal expands, or a semiconductor failing at temperature
- How to confirm it
- Heat gun on low, about 15 cm away, on one suspect area at a time while monitoring the signal. Reproducing it deliberately is faster than waiting for it.
- What fixes it
- Repair the joint or renew the component the heat test implicates. A cold bench test on this fault passes and proves nothing.
-
Present when the car is cold or in cold weather, gone once warm
- Likely cause
- The opposite thermal case — a joint that closes as it expands, or a component out of tolerance cold
- How to confirm it
- Freeze spray one component at a time while monitoring. A fault that appears or clears as a specific part is chilled has been localised.
- What fixes it
- Repair or renew what the cold test names. Both thermal directions are real and they need opposite tools.
-
Follows rain, washing or damp mornings
- Likely cause
- Damp bridging two pins, or corrosion that is only a bad connection when wet
- How to confirm it
- Spray one area at a time with a hose or bottle while monitoring live data. This is one of the few faults a driver can help reproduce on a driveway.
- What fixes it
- Dry, clean and seal the connector, and repair whatever route lets the water in. See the wet-weather entry in this vocabulary.
-
Nothing provokes it in a workshop
- Likely cause
- Not absent — merely not reproducible on a ramp, which is a different thing
- How to confirm it
- Fit a data logger and drive the car normally until it happens, then read the log around the event. Read stored freeze-frame data before clearing anything.
- What fixes it
- Repair what the log or frame names. This is the case where the driver's written notes are worth more than any bench test.
-
Several unrelated systems affected at the same moments
- Likely cause
- Supply or earth rather than any of the named systems — modules misbehave together when voltage sags
- How to confirm it
- Voltage-drop test the main earths and supply under load rather than at rest. A resting continuity check passes a joint that fails under current.
- What fixes it
- Remake the earth or repair the supply, then clear and re-scan. Only what returns is real.
Codes that produce this symptom (359)
Listed with the codes that most typically present this way first — the likeliest place to start.
- P0074 Ambient Air Temperature Sensor Circuit A Intermittent/Erratic Typical of this code Low
- P0099 Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic Bank 1 Typical of this code Moderate
- P0104 Mass or Volume Air Flow Sensor A Circuit Intermittent Typical of this code Moderate
- P0109 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent Typical of this code Moderate
- P0114 Intake Air Temperature Sensor 1 Circuit Intermittent Bank 1 Typical of this code Moderate
- P0119 Engine Coolant Temperature Sensor 1 Circuit Intermittent/Erratic Typical of this code Moderate
- P0124 Throttle/Pedal Position Sensor/Switch A Circuit Intermittent Typical of this code Stop driving High
- P0184 Fuel Temperature Sensor A Circuit Intermittent Typical of this code Moderate
- P0189 Fuel Temperature Sensor B Circuit Intermittent Typical of this code Moderate
- P0194 Fuel Rail Pressure Sensor Circuit Intermittent/Erratic Bank 1 Typical of this code Stop driving High
- P0199 Engine Oil Temperature Sensor A Circuit Intermittent/Erratic Typical of this code Moderate
- P0224 Throttle/Pedal Position Sensor/Switch B Circuit Intermittent Typical of this code Stop driving High
- P0229 Throttle/Pedal Position Sensor/Switch C Circuit Intermittent Typical of this code Stop driving High
- P0233 Fuel Pump Secondary Circuit Intermittent Typical of this code Stop driving High
- P0255 Injection Pump Fuel Metering Control A Intermittent (Cam/Rotor/Injector) Typical of this code Stop driving High
- P0260 Injection Pump Fuel Metering Control B Intermittent (Cam/Rotor/Injector) Typical of this code Stop driving High
- P0323 Ignition/Distributor Engine Speed Input Circuit Intermittent Typical of this code Stop driving High
- P0329 Knock/Combustion Vibration Sensor A Circuit Intermittent Typical of this code Moderate
- P0334 Knock/Combustion Vibration Sensor B Circuit Intermittent Typical of this code Moderate
- P0339 Crankshaft Position Sensor A Circuit Intermittent Typical of this code Stop driving Critical
- P0344 Camshaft Position Sensor A Circuit Intermittent Bank 1 or Single Sensor Typical of this code Stop driving High
- P0349 Camshaft Position Sensor A Circuit Intermittent — Bank 2 Typical of this code Stop driving High
- P0369 Camshaft Position Sensor B Circuit Intermittent — Bank 1 Typical of this code Stop driving High
- P0373 Timing Reference High Resolution Signal A Intermittent or Erratic Pulses Typical of this code Stop driving High
- P0378 Timing Reference High Resolution Signal B Intermittent or Erratic Pulses Typical of this code Stop driving High
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Others with this symptom
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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