Holden Commodore Problems

All the V6 Commodores from this era used much the same automatic transmission, a four-speed unit. While most of these units were identical, there were some detail differences across the years, so make sure you get the transmission with the correct number of electrical pins to be compatible with the wiring loom in your car.

It shouldn’t matter whether the replacement transmission came from a car with a floor-shift; it should still hook up to your column shift mechanism with no problems. You might have to swap a few bits and pieces involved in the shifter mechanism to mate it all, but you’ll be able to make it work.

Many mechanics at this point would put their money on a bad earth somewhere on the car. Even though the LED light is working, the car’s computer thinks otherwise and, since LEDs draw so little current in the first place, they can be a bit hard to diagnose. Even so, the fast flashing suggests that there’s definitely a problem. To be honest, an auto electrician is probably your best bet at this stage.

Some owners of older cars have found that switching to LED headlight globes can cause the car to think that there’s a blown light somewhere as the current being drawn by the LEDs is so small compared with the normal globes the car came with. Fundamentally, the computer can’t see the current that should be being drawn when the lights are on, and fires the check-light warning symbol. You may find it’s the LED indicator light unit itself that is faulty. These can develop random failures in the internal circuitry that controls them.

The first thing to do, though, is to try the home computer reset which involves disconnecting the battery overnight and seeing if that calms the computer’s nerves. It might not work, but it’s free to try.

An automatic gearbox relies on fluid pressure as well as volume to make everything work as it should. So, if the level of fluid is correct, you then need to move on to the pump and accumulators involved to ensure that the correct hydraulic pressure is being applied to the bands and clutches that actually apply drive to the gears and physically move the car.

Your problem could be something as simple as a worn pump, but it could also indicate internal wear and tear that requires a complete transmission rebuild. A transmission specialist is your best bet. The good news is that this is a common and well understood transmission, so finding an expert shouldn’t be difficult.

We have seen this problem before in at least one other ZB Commodore, so you’re definitely not on your own. The problem is very possibly caused by a misalignment of the micro-switch that detects the car is, indeed, in Park, and allows it to be powered down. If the computer can’t see the correct signal from this micro-switch or sensor, it assumes the car is not ready to be locked and left.

Given that yours is not the only example of this, perhaps your auto electrician has seen this before and will know what the fix is. Even if they’re not familiar with the problem, a good auto sparky should be able to sort this. If not, a transmission specialist would be your next port of call.

A manifold leak will throw the engine’s fuel-air ratio out the window and can cause poor cold running and hard starting. The old school way of checking for a vacuum leak is to get the engine idling and then spray either carburettor cleaner (or something else flammable) around the intake area of the engine. If the engine suddenly picks up revs, you almost certainly have a vacuum leak. But be careful, spraying flammable stuff around a running engine comes with a fire risk.

The other thing to check would be the throttle body and the sensor attached to it that tells the computer how much throttle has been applied. Again, these can start to give false readings, throwing the fuel-air mixture out.

Before you do either of those things (replace the engine or the whole car) find out where the coolant is leaking from. You might find that it’s a simple case of a leaking hose or a worn out water pump that is causing the leak. If that’s the case, it could be fixed for a few hundred dollars or perhaps even less. Even if the problem is a rotted welch plug or a blown head gasket, the cost to fix it won’t be anywhere near as high as replacing the engine.

On top of that, you know the history of the engine you have, while a second-hand engine can be a bit of a lucky-dip: You might get a good one, you might not.

Modern automatic transmissions are pretty complex things and there’s a lot that can go wrong from the simple low fluid level to the catastrophic like a broken torque converter or failed valve body, gearset, oil pump or clutch pack.

But mechanics know that the first sign of this transmission failing totally is a refusal to select Drive. Take the car to a transmission specialist who will have seen these symptoms before and will have a pretty good idea of what’s going on before they even lay a spanner on the car. And be prepared to replace the transmission as the only proper fix.

A second-hand transmission from a wrecked Commodore might be an option, but only if you can prove that the unit has done moderate mileage and, therefore, is probably not about to produce the same symptoms as yours already has.

The answer is probably a pretty simple one in terms of what’s causing it. The warning light is to remind you to leave the car with Park engaged. So, the gear selector will have a tiny sensor or micro-switch that detects the selector in the Park position which is then conveyed to the car’s body computer. But if the sensor or switch is faulty or not adjusted correctly, the computer will think the car is not in Park and will light up the warning to alert you. The intermittent nature of the fault is what makes us think this is the case, combined with the fact that a quick flick of the T-bar button is enough to make the warning disappear.

So much for the cause, because the fix might be a bit more complicated. Depending on where the sensors and switches live, you may need to disassemble more of the car than would seem necessary to fix such a seemingly small problem. An auto electrician should be able to make sense of it.

You need to go back to basics here. Check that the battery is connected firmly and that all the connections and low-voltage leads that power and trigger the starter motor are in their correct places and receiving power. Don’t forget to check for earth straps and cables that might have been left off in the reassembly process, too.

If the car is getting power (and the dashboard lights suggest it is) then there’s a problem between the ignition key and the starter motor. Tackle it methodically, checking for power (a test lead or multimeter will be invaluable for this) as you work your way towards the starter motor and you’ll probably find it’s something really simple and basic. Make sure the fuse or relay for the starter motor hasn’t been fried during the gearbox swap, too.

Presumably the car makes this noise when you hit a bump or undulation. The Commodore’s front end is not particularly complex and is, in fact, a pretty standard MacPherson strut set-up.

With that in mind, there are only so many things that could cause the front end to bang or rattle, including a worn ball-joint, tie-rod end, or suspension bush. But don’t forget about the bushes in the steering rack, too, as these can contribute to a noise from the front end.

If all the suspension checks out, then you need to go a bit deeper into things like the cross-member mounts, engine mounts and even wheel bearings. Any wear or play in these components will cause a clunk in the right circumstance.

If none of that helps then you need to look beyond the suspension and into areas like a loose battery tray in the engine bay or even a loose piece of trim or sheet metal somewhere on the car. Exhaust heat shields are prime candidates for this, as are the metal shields at the back of each brake disc.