Symptom
Multiple unrelated warning lights
Several warning lights for unconnected systems appear at once — ABS, traction control, engine, transmission, steering. Counter-intuitively this usually indicates one fault rather than many, and most often an electrical supply problem: modules do not simply stop when voltage sags, they misbehave, so a corroded battery terminal or a failing alternator produces a page of faults in systems that are working perfectly. Have the battery and charging system tested before anything is diagnosed individually.
Also described as: lots of warning lights, all the lights came on, dashboard lit up, multiple faults, every light on, christmas tree dashboard, همه چراغها روشن شد, چند چراغ هشدار, کل چراغها روشن, muchas luces encendidas, varios testigos encendidos, todas luces encendidas, tablero lleno de luces, لمبات كثيرة مضيئة, كل العلامات ظهرت, التابلوه امتلأ إشارات
Some causes mean you should stop driving
31 of the 815 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
Several lamps at once almost always means one fault, and the fault is usually electrical supply. This is counter-intuitive enough that it is worth stating plainly: modules do not simply switch off when voltage sags, they misbehave — they lose communication, fail their own self-tests, and set codes describing faults that do not exist. So a corroded battery terminal produces a page of faults in systems that are working perfectly.
The mechanism is worth understanding because it changes the order of work entirely. Each module monitors its own supply and its own network. Below the voltage they are designed for, some drop off the bus while others stay on it — and a module that cannot hear its neighbour reports exactly that, truthfully. The resulting code list is a description of the symptom, not the cause, and chasing it component by component is how a supply fault turns into a week of work.
So: test the battery and charging system before diagnosing anything individually. A conductance test, the charging voltage at the terminals with the engine running, and a voltage-drop check on the main earths. A poor earth is the version most often missed, because everything appears to have power and only the return path is bad.
Two other single causes produce the same picture. A failing alternator whose output collapses or whose ripple is high upsets every module on the car at once. And water in a connector or a module — after a screen washer leak, a blocked bulkhead drain, or driving through standing water — corrupts several networks from one place. Read the codes for a common thread rather than a common part: if they are mostly communication faults, look at supply and network; if they are mostly sensor faults across unrelated systems, look at earths.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Lights arrived together, engine cranks slowly or the battery is old | Low system voltage making every module misbehave — one fault reported by many | Conductance test the battery and measure charging voltage at the terminals with the engine running. Read codes but do not act on them individually yet. | Renew the battery, remake the terminals, and register it where the car has energy management. Clear the codes and re-scan; only what returns is real. |
| Lights that come and go, headlights dimming or flickering | Charging system — a failing alternator, high AC ripple, or a slipping belt | Measure charging voltage under load and AC ripple at the alternator B+ — more than about 0.5 V AC points at failed diodes. Check belt tension and the tensioner. | Renew the alternator or the belt and tensioner. High ripple upsets modules across the car and is easy to miss with a voltmeter alone. |
| Codes are mostly communication or 'no message received' faults | A network problem — a module off the bus, a damaged bus wire, or a gateway fault | Identify which modules are missing and look for what they share — a connector, a fuse, an earth. A wiring diagram beats guessing here. | Repair the shared connection. A single failed module can also take the bus down, so the missing one is not automatically the faulty one. |
| Started after heavy rain, a wash, or driving through water | Water in a connector or a module — one entry point corrupting several systems | Inspect connectors in the affected area and the module locations, and check bulkhead and scuttle drains. Look for green corrosion and water staining. | Dry, clean and seal, and clear the drain that let the water in. Sealing without fixing the ingress is temporary. |
| Appeared immediately after a jump start or battery work | A voltage transient or a reversed connection during the work, or simply the modules seeing an interruption | Retrace what was done. Many of these codes are historic and clear on their own; scan, clear, and re-scan after a drive. | Clear and re-scan. Only diagnose what returns — the rest were recorded during the interruption. |
| Voltage tests good, lights persist, codes span unrelated sensors | A poor earth — everything has supply and the return path is bad | Voltage-drop test the main earth straps under load rather than checking continuity at rest. A resting continuity check passes an earth that fails under current. | Clean and remake the earth points, or renew the strap. Re-measure the drop to prove it has gone. |
-
Lights arrived together, engine cranks slowly or the battery is old
- Likely cause
- Low system voltage making every module misbehave — one fault reported by many
- How to confirm it
- Conductance test the battery and measure charging voltage at the terminals with the engine running. Read codes but do not act on them individually yet.
- What fixes it
- Renew the battery, remake the terminals, and register it where the car has energy management. Clear the codes and re-scan; only what returns is real.
-
Lights that come and go, headlights dimming or flickering
- Likely cause
- Charging system — a failing alternator, high AC ripple, or a slipping belt
- How to confirm it
- Measure charging voltage under load and AC ripple at the alternator B+ — more than about 0.5 V AC points at failed diodes. Check belt tension and the tensioner.
- What fixes it
- Renew the alternator or the belt and tensioner. High ripple upsets modules across the car and is easy to miss with a voltmeter alone.
-
Codes are mostly communication or 'no message received' faults
- Likely cause
- A network problem — a module off the bus, a damaged bus wire, or a gateway fault
- How to confirm it
- Identify which modules are missing and look for what they share — a connector, a fuse, an earth. A wiring diagram beats guessing here.
- What fixes it
- Repair the shared connection. A single failed module can also take the bus down, so the missing one is not automatically the faulty one.
-
Started after heavy rain, a wash, or driving through water
- Likely cause
- Water in a connector or a module — one entry point corrupting several systems
- How to confirm it
- Inspect connectors in the affected area and the module locations, and check bulkhead and scuttle drains. Look for green corrosion and water staining.
- What fixes it
- Dry, clean and seal, and clear the drain that let the water in. Sealing without fixing the ingress is temporary.
-
Appeared immediately after a jump start or battery work
- Likely cause
- A voltage transient or a reversed connection during the work, or simply the modules seeing an interruption
- How to confirm it
- Retrace what was done. Many of these codes are historic and clear on their own; scan, clear, and re-scan after a drive.
- What fixes it
- Clear and re-scan. Only diagnose what returns — the rest were recorded during the interruption.
-
Voltage tests good, lights persist, codes span unrelated sensors
- Likely cause
- A poor earth — everything has supply and the return path is bad
- How to confirm it
- Voltage-drop test the main earth straps under load rather than checking continuity at rest. A resting continuity check passes an earth that fails under current.
- What fixes it
- Clean and remake the earth points, or renew the strap. Re-measure the drop to prove it has gone.
Codes that produce this symptom (815)
Listed with the codes that most typically present this way first — the likeliest place to start.
- C0020 ABS Pump Motor Control 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
- C05A4 Wheel Speed Sensors Supply Circuit Low Typical of this code High
- P0560 System Voltage Typical of this code Moderate
- P0561 System Voltage Unstable Typical of this code Moderate
- P0562 System Voltage Low Typical of this code Moderate
- P0563 System Voltage High Typical of this code High
- P0600 Serial Communication Link Typical of this code Moderate
- P060C Internal Control Module Main Processor Performance Typical of this code Stop driving High
- P0641 Sensor Reference Voltage A Circuit Open Typical of this code High
- P0642 Sensor Reference Voltage A Circuit Low Typical of this code High
- P0643 Sensor Reference Voltage A Circuit High Typical of this code High
- P0651 Sensor Reference Voltage B Circuit Open Typical of this code High
- P0652 Sensor Reference Voltage B Circuit Low Typical of this code High
- P0653 Sensor Reference Voltage B Circuit High Typical of this code High
- P065A Generator System Performance Typical of this code High
- P0697 Sensor Reference Voltage C Circuit Open Typical of this code High
- P0698 Sensor Reference Voltage C Circuit Low Typical of this code High
- P0699 Sensor Reference Voltage C Circuit High Typical of this code High
- P06A3 Sensor Reference Voltage D Circuit/Open Typical of this code High
- P06D3 Sensor Reference Voltage E Circuit Low Typical of this code High
- P0720 Output Shaft Speed Sensor Circuit Typical of this code High
- P0722 Output Shaft Speed Sensor Circuit No Signal 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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- The car — make, model, year and engine. The same fault behaves differently on each.
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