Symptom
Fault only appears in wet weather
It plays up in the rain, after a wash, or on a damp morning, and behaves perfectly the rest of the time. Water does not need to get inside anything for this — damp is enough to bridge two pins with a film that conducts just well enough to confuse a signal, and a connector full of green corrosion is only a bad connection when it is wet. The places to suspect are the ones that get sprayed: behind the front bumper, under the wheel arches, along the sills. A hose pipe is a legitimate diagnostic tool here, and it is one of the few faults a driver can help reproduce on the driveway.
Also described as: only when wet, only in the rain, after washing the car, damp weather fault, plays up in the rain, only when its damp, فقط در هوای بارانی, وقتی رطوبت هست, بعد از کارواش, solo falla con lluvia, pasa cuando llueve, solo con humedad, falla cuando llueve, solo cuando llueve, falla lloviendo, solo lloviendo, فقط وقت المطر, المشكلة بالجو الرطب, تحصل لما تمطر
Some causes mean you should stop driving
3 of the 68 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
Water does not need to get inside anything for this. Damp is enough to bridge two pins with a film that conducts just well enough to confuse a signal, and a connector full of green corrosion is only a bad connection when it is wet — dry, the same connector passes every test somebody performs on a ramp under cover.
The places to suspect are the ones that get sprayed: behind the front bumper, under the wheel arches, along the sills, and anywhere a harness runs low. Add the ones that get wet from above — the scuttle at the base of the windscreen, where blocked drains overflow into the bulkhead, and door apertures where a membrane has come unstuck.
A hose pipe is a legitimate diagnostic tool here, and it is one of the few faults a driver can help reproduce on the driveway. The discipline is one area at a time, working from the lowest suspect upward, with live data or a meter watching the affected circuit. Wetting the whole car proves only that it is the car.
Ignition secondary is the other population and it fails differently. High-voltage insulation that has hardened or cracked lets the spark track to earth through a damp film instead of jumping the plug gap, so the engine misfires in the rain and runs perfectly in a dry spell. Look for tracking marks, and look at the engine in the dark with it running — a corona discharge is visible and unmistakable.
And water rarely announces itself where it entered: it runs along a loom to the lowest connector and sits there, so the fault appears at a part that never got wet.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Misfire in rain, perfect in dry weather, petrol engine | Ignition secondary tracking to earth through a damp film rather than jumping the plug gap | Inspect leads, boots and coil packs for tracking marks; run the engine in the dark and look for a visible corona. A spray bottle reproduces it on demand. | Renew leads, boots or coils. Tracking marks are permanent damage to the insulation. |
| Electrical faults that follow rain or a wash | Damp bridging pins, or corrosion that only becomes a bad connection when wet | Spray one area at a time, lowest first, while monitoring live data. Wetting everything at once tells you nothing about where. | Dry, clean and seal the connector, and repair the route that lets water reach it. |
| Damp carpets, or a musty smell, alongside the electrical fault | A blocked scuttle or sunroof drain overflowing into the bulkhead, or a door membrane come unstuck | Check the drains rather than the connectors first. Wet carpet localises the entry point better than any electrical test. | Clear the drains and reseal the membrane, then dry and repair the affected connectors. |
| Fault appears at a component that plainly never got wet | Water has run along the loom to the lowest connector — the entry point is elsewhere and usually higher | Trace the harness upward from the affected connector looking for the entry. Follow the loom, not the symptom. | Seal the entry and repair the connector. Sealing the connector alone means it fills again. |
| Started after a jet wash rather than rain | Water forced past a seal that ordinary rain never challenges | Establish the timing. Pressure-washing near the engine bay, wheel arches or under-bumper connectors is a common trigger. | Dry and reseal. Advise keeping the lance away from connectors and seals — this one recurs otherwise. |
| Only in wet weather AND only over bumps | A connector that is both damp and moving — corrosion plus a marginal mechanical fit | Combine the two tests: spray the area, then wiggle it while monitoring. Neither alone will find it reliably. | Renew the connector rather than cleaning it. A joint failing on two counts will not be rescued by drying. |
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Misfire in rain, perfect in dry weather, petrol engine
- Likely cause
- Ignition secondary tracking to earth through a damp film rather than jumping the plug gap
- How to confirm it
- Inspect leads, boots and coil packs for tracking marks; run the engine in the dark and look for a visible corona. A spray bottle reproduces it on demand.
- What fixes it
- Renew leads, boots or coils. Tracking marks are permanent damage to the insulation.
-
Electrical faults that follow rain or a wash
- Likely cause
- Damp bridging pins, or corrosion that only becomes a bad connection when wet
- How to confirm it
- Spray one area at a time, lowest first, while monitoring live data. Wetting everything at once tells you nothing about where.
- What fixes it
- Dry, clean and seal the connector, and repair the route that lets water reach it.
-
Damp carpets, or a musty smell, alongside the electrical fault
- Likely cause
- A blocked scuttle or sunroof drain overflowing into the bulkhead, or a door membrane come unstuck
- How to confirm it
- Check the drains rather than the connectors first. Wet carpet localises the entry point better than any electrical test.
- What fixes it
- Clear the drains and reseal the membrane, then dry and repair the affected connectors.
-
Fault appears at a component that plainly never got wet
- Likely cause
- Water has run along the loom to the lowest connector — the entry point is elsewhere and usually higher
- How to confirm it
- Trace the harness upward from the affected connector looking for the entry. Follow the loom, not the symptom.
- What fixes it
- Seal the entry and repair the connector. Sealing the connector alone means it fills again.
-
Started after a jet wash rather than rain
- Likely cause
- Water forced past a seal that ordinary rain never challenges
- How to confirm it
- Establish the timing. Pressure-washing near the engine bay, wheel arches or under-bumper connectors is a common trigger.
- What fixes it
- Dry and reseal. Advise keeping the lance away from connectors and seals — this one recurs otherwise.
-
Only in wet weather AND only over bumps
- Likely cause
- A connector that is both damp and moving — corrosion plus a marginal mechanical fit
- How to confirm it
- Combine the two tests: spray the area, then wiggle it while monitoring. Neither alone will find it reliably.
- What fixes it
- Renew the connector rather than cleaning it. A joint failing on two counts will not be rescued by drying.
Codes that produce this symptom (68)
Listed with the codes that most typically present this way first — the likeliest place to start.
- C0044 Brake Pressure Sensor A Typical of this code Moderate
- C0045 Brake Pressure Sensor B Typical of this code Moderate
- C0046 Brake Pressure Sensor A/B Typical of this code Moderate
- C0051 Steering Wheel Position Sensor Typical of this code Moderate
- C0052 Steering Wheel Position Sensor Signal A Typical of this code Moderate
- C0053 Steering Wheel Position Sensor Signal B Typical of this code Moderate
- C0054 Steering Wheel Position Sensor Signal C Typical of this code Moderate
- C0055 Steering Wheel Position Sensor Signal D Typical of this code Moderate
- C0061 Lateral Acceleration Sensor Typical of this code Moderate
- C0062 Longitudinal Acceleration Sensor Typical of this code Moderate
- C0063 Yaw Rate Sensor Typical of this code Moderate
- C0064 Roll Rate Sensor Typical of this code Moderate
- C0069 Yaw Rate/Longitude Sensors Typical of this code Moderate
- C006A Multi-axis Acceleration Sensor Typical of this code Moderate
- C006C Stability System Typical of this code Moderate
- C0073 Delivered Driving Torque Typical of this code Moderate
- C0074 Requested Driving Torque Typical of this code Moderate
- C0076 PWM for Traction Control Typical of this code Moderate
- C0089 TCS Disable Switch Typical of this code Moderate
- C0529 Steering Angle Sensor Module Missing Calibration Typical of this code Moderate
- C053D Brake Pressure Sensor A Range/Performance Typical of this code Moderate
- C0542 Brake Pressure Sensor B Circuit Low Typical of this code Moderate
- C0543 Brake Pressure Sensor B Circuit High Typical of this code Moderate
- C055F BSCM/EBBC Hydraulic Unit Performance Typical of this code High
- C05A4 Wheel Speed Sensors Supply Circuit Low Typical of this code 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.
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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.
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