A scan tool reads the fault codes and live data from the car's modules, and that tells us where to look. Then we prove the fault on the circuit itself with a multimeter or an oscilloscope. A code can point at a sensor when the real problem is the wiring or the earth behind it, so we test before anything is replaced.
That is what car electrical diagnostics is for. Car electrical fault finding done properly means parts are not swapped blindly, you are not paying for a guess, and the repair we quote is for the fault we actually found. Call 07 3566 2108 or use the quote form on this page to book the vehicle in.
Car electrical fault finding: what we track down
These are common faults that bring cars into a workshop. Each one needs a different test, which is why we start with the symptoms and not the parts.
Cars that won't crank or won't fire
A car that won't crank is a different problem from one that cranks and won't fire. No crank points us at the battery, the starter circuit, the ignition switch or the immobiliser. Crank but no start means checking for spark, fuel pump and injector signals, and a valid key code. We test each signal in turn until one is missing, and we check the starter motor feed and earth for voltage drop while the engine is cranked, because a worn cable can fool a battery test.
Battery drain and parasitic draw
A battery that is flat after a night or a weekend is usually being drained by something that never switches off. It could be a module that will not go to sleep, a stuck relay, a boot light or aftermarket wiring. We measure the parasitic draw with the car locked, then pull circuits one at a time until the draw drops. Once the circuit is found, we fix the wiring or the faulty part.
Warning lights and module faults
A warning light is the car telling you a module saw something wrong. We read the stored codes, then watch live data to see whether the reading makes sense. CAN-bus communication faults, where modules stop talking to each other, need the network tested, not just the code cleared and the light switched off. Clearing a code without finding the cause only hides the fault until it returns, so we also check the power and earth supply to the module.
Lighting, windows and central locking
Dead headlights, a window that stops halfway or a door that will not lock are usually a switch, a motor, a relay or a broken wire. In doors the culprit is often the loom flexing at the hinge. We check for power and earth at the component first, then work back along the circuit to find the break. Indicators, brake lights and wipers fall in here too. We retest each function after the repair.
Wiring, fuses and earth faults
A fuse that keeps blowing is protecting a circuit with a short. A corroded earth strap can make lights dim, gauges drift and starting sluggish. A chafed wiring loom can cause faults that come and go with the bumps. We find the damaged section, repair it properly and check the circuit afterwards. Swapping the fuse for a bigger one is never the fix, because the fuse is what stops the wiring overheating. We trace the short, repair the cause and protect the circuit the way it was designed.
How auto electrical diagnostics in Logan find the fault
Every diagnosis follows the same four steps. It keeps the work honest and means you see what was tested before you decide on a repair.
- 1
Note the symptoms
We ask when the fault happens, whether it follows rain, heat, bumps or a cold start, and what has been fitted or repaired lately. We also check what the dash is showing. The pattern of an intermittent fault is often the best clue we get.
- 2
Scan and read live data
We connect an OBD diagnostics scan tool and read stored codes from every module we can reach. Codes are a starting point, not the answer. Live data shows what each sensor and module is doing while the fault is present, which tells us whether a part is failing or being fed bad information.
- 3
Prove it on the circuit
We test the suspect circuit with a multimeter or scope. A voltage drop test shows resistance in a feed or earth, a continuity test finds breaks in a wiring loom, and a scope shows signals that a meter would miss. The fault is confirmed before any part is changed.
- 4
Quote, repair and road test
You get a written quote for the repair before we start. Once it is done, we retest the circuit and road test the car to confirm the fault is gone. If the original symptom needs the car to be driven, we drive it.
Book the vehicle in and we'll test it and price the repair before any work starts.
Electrical faults in Logan cars and utes
Logan's population was 403,515 at 30 June 2025, up 3.1% on the year, which made it Queensland's second-fastest-growing council area. The city covers 957 km², so plenty of local trips cover real distance.
Much of that driving is on the Pacific Motorway, which runs through Springwood and Loganholme on its way to the Gold Coast. Stop-start traffic on the M1 asks a lot of the charging system and the battery.
Heat adds to it. The NRMA notes that temperatures above 30°C can speed up a battery's internal chemical reactions and shorten its life, and that is general motoring advice, not specific to south-east Queensland. Add tradie utes and 4WDs loaded with lights, winches and extra accessories, and the wiring has plenty to put up with. That is where many auto electrical repairs in Logan start.
What you get from car electrical diagnostics
Whatever the fault turns out to be, you leave with a clear answer and the facts to make a decision.
A clear finding
We tell you what failed, where it is on the car and which test proved it. You are not handed a code number and a shrug. If a part is faulty we say so, and if the fault was a loose connection or a corroded earth we show you the evidence for that too.
Options before repairs
Often a fault has more than one fix, such as repairing a section of wiring loom or replacing the whole component. We explain the choices and the trade-offs, and quote the repair in writing. Nothing gets started until you have agreed to it, so the choice stays with you, whichever repair you pick.
Repairs checked after
When the repair is finished we retest the circuit that failed and road test the car. That is how we confirm the original symptom is gone, and not just that the new part is fitted. Faults that only appear in certain conditions get a longer drive to recreate them, and we retest before handing back the keys.
How much does it cost to diagnose a car electrical fault?
The cost of diagnosing a car electrical fault depends on how hard the fault is to find, not on the badge on the bonnet. As a guide, auto electrical labour typically runs about A$90 to A$150 an hour (ServiceTasker, Feb 2026), and a wiring or fault repair typically costs from about A$150 to A$900 (The Quote Yard, Jun 2026). Every fault is different, so the final quote is given on inspection. Use the form beside this page to get a free written quote.
Intermittent or constant fault
A fault that is always there can be tested straight away. One that comes and goes may need the car left with us, or several test sessions, until the fault shows itself on the meter or scope.
Vehicle networks
Late-model cars run many ECU modules on a CAN-bus network. More modules means more data to read and more places a communication fault can hide, so the testing takes longer.
Past repairs and accessories
Aftermarket wiring, such as lights, audio, trailer plugs and alarms, has to be traced and understood before we can rule it in or out.
Getting at the wiring
Some circuits sit behind trims, under the dash or beneath the seats. The time it takes to remove and refit those parts is part of the job, and we allow for it in the quote.
Auto electrical diagnostics FAQs for Logan
Why does my car crank but not start?
A car that cranks but does not start is missing fuel, spark or a valid immobiliser signal. The engine is turning, so the battery and starter are usually working. We check for spark, fuel pump and injector signals, and whether the immobiliser is recognising the key, to find which one is missing.
Why won't my car start when the battery is fine?
When a car won't start with a good battery, it usually has a fault in the starter circuit, the ignition switch, the immobiliser or an earth. The battery can show full voltage but still fail to deliver current through a corroded terminal or a weak earth strap. We test voltage drop through the circuit under load to find where the power is being lost.
Why does my car start and then die straight away?
A car that starts and then dies straight away is often not getting something it needs after the first second. That can be an immobiliser not recognising the key, a failing fuel pump relay or a crank sensor signal dropping out. We scan for codes and test those circuits while the engine runs.
Why does my car only start sometimes?
A car that only starts sometimes usually has an intermittent fault, such as a loose connection, a worn ignition switch, a failing starter solenoid or a weak battery. These faults hide when the car is in the workshop. That is why we test while the fault is happening and note when it occurs.
Why would a car completely shut off while driving?
A car can shut off while driving when the charging system fails and drains the battery, when a main earth or ignition feed comes loose, or when a sensor drops out. Pull over safely and do not keep restarting it. We test the charging output and the main feeds and earths to find the cause.
How can you tell if your car has an electrical problem?
You can tell a car has an electrical problem from warning lights, flickering headlights, repeatedly blown fuses, a burning smell or accessories that act up on their own. Slow cranking and a dash that resets are also signs. If any of these appear, have the car tested before a small fault turns into a bigger one.
What causes a car to lose all electrical power?
A car loses all electrical power when something cuts the supply at the source. That is commonly a loose or corroded battery terminal, a failed main fuse, a faulty ignition switch or a flat battery. We start at the battery and main earth, then work through the main feeds to find where the power stops.
