[Old Blue]

Ok. So I drive home from work like I do every day and park the car in the driveway. About 45 minutes later, I go out and put the key in the ignition and turn it....but nothing. I noted that the interior lights were on but the light illuminating the transmission gear setting was not lit, the headlights that are daytime running lights didn't come on and when you turn the key there is no response. The battery is good and the terminal connections are good and I don't see any blown fuses in the relay box.

Anyone got a suggestion or advice? The car is a '03 with the 2.5 and is an auto trans. Theres about 240,000 on the odometer.

 

[BoarderM]

How do you know the battery is good? It should be 12.6 volts at the terminals. The interior lights may still work even though the battery is drained to the point that it wouldn't start your car.

 

[Old Blue]

Thanks for responding Boarder. I had the battery bench checked to make sure it was good and it was. Still didn't make a difference so loaded it up on a friends roll back to haul down to his shop. As I was taking it off the back of the truck, I turned on the key to release the steering and noted that the trans position light was on so I turned the key to start and low and behold it started. Used it all day today without a problem. I'm suspecting I have a short somewhere but heaven only knows where.

 

[bobfromvienna]

I went to Advanced Auto Parts and bought a diagnostic tool. Hook it up to your car and see if any codes show up.

 

[CNY_Dave]

Always try neutral too, helps show up a bad safety switch.

 

[DavidPeab]

Sounds like a ground fault. Check the negative battery cable, especially where it attaches to the body. Sometimes a bit of corrosion there can reduce a circuit enough to cause intermittent starting problems. Although that might not explain the dome light. Meh...

 

[Old Blue]

I went to Advanced Auto Parts and bought a diagnostic tool. Hook it up to your car and see if any codes show up.

Thats a good suggestion. How much did that set you back?

 

[Old Blue]

Always try neutral too, helps show up a bad safety switch.

Yep tried that. Had to use the pop out by-pass to get it into neutral.

 

[Old Blue]

Sounds like a ground fault. Check the negative battery cable, especially where it attaches to the body. Sometimes a bit of corrosion there can reduce a circuit enough to cause intermittent starting problems. Although that might not explain the dome light. Meh...

That all looks good right now. I'm not sure I'll be able to find the short until it (or if it!) happens again. But I'm convinced it's gotta be a short somewhere in the system. It's just where to start looking at this point.

 

[dryvby]

Anti theft system on the vehicle?

 

[Old Blue]

Anti theft system on the vehicle?

No sir. I don't have one of those.

 

[CNY_Dave]

Sometimes one gets installed and 'abandoned', wires and box tucked up under the dash and forgotten.

 

[plain OM]

A short would most likely blow a fuse -- most circuits are protected this way. However, an open circuit, such as a break in a wire, could cause something to not work.

The link to the transmission position indicator in the instrument panel might be a clue. The lights in the instrument panel behind the P, R, D indicators are turned on according to the position of the inhibitor switch. This is on the right side of the transmission, and controls the electronic switching to tell the transmission which gear it should be in. There's a large connector at the switch and a cable (harness) that goes up to the engine compartment.

If the connector at the inhibitor switch is loose or is making bad connections, the necessary connections to turn on the indicator lights in the instrument panel will be missing.

Along these same lines, the inhibitor switch has contacts that are in the starter circuit. These contact are closed when the gear is in P or N, thereby allowing the starter to function only in those gears. Once again, if the circuit isn't being closed, the starter won't run.

It's not likely that all the contacts in the switch itself would be bad, but a loose connector or a switch that isn't moving properly (caused by build up of rust/dirt on the exposed mechanism) could cause this. Given that the connectors at the switch and higher up on the harness are common to both symptoms, I'd have a look.

A question: When the key was at On and the transmission indicators were all off, were any of the other instrument panel lights (illumination or warning) lit? If they were, that would eliminate the power source that is common to the transmission indicators and the rest of the panel lights.

 

[Old Blue]

The dashboard indicators all lit with the exception of the trans indicators. I've been using this car as my daily commuter and putting on about 75 miles a day to and from work so I'd hate to wait for the problem to re-occur to find the issue.

 

[CNY_Dave]

What I recall of the schematic, that narrows it down quite a bit. Power to TCU, connections from TCU to trans connector (the one that goes to the interlock switch), or the interlock switch itself. The interlock switch is the big plastic switch that sits on the side of the trans where the shift cable attaches.

 

[plain OM]

The dashboard indicators all lit with the exception of the trans indicators.

That means the power to the combination meter (instrument panel) lighting is good, and the problem is unique to the AT part of the circuit.

I've attached the schematic for the AT Control and the Starter.

Looking at the AT Control, if the lights in the instrument panel other than the P,R,D etc are working, then the problem is pretty well isolated to the circuit that turns the P,R,D, etc lights on or off, which is the inhibitor switch. The switch controls the ground for each light, so that in any one position of the switch, the corresponding light should be on. If the switch connector is loose, then the ground will not be completed and the individual lights will not work.

Now look at the Starter diagram. Here again, the inhibitor switch is in the circuit, linking the power source (ST) to the starter motor solenoid. The switch has to be in the P or N position (and making the related connections) for the starter to work. Note that it's the same connectors as in the AT control diagram, T7 and T3, that are critical in this circuit.

The fact that the P,R,D etc lights weren't on when the car would not start, but as soon as the lights came on the car started, points to something common to the two. The inhibitor switch, and more significantly, the connectors, are candidates. There might be others, but at this stage I can't identify ones that would cause these same symptoms at the same time.

 

[Old Blue]

Thanks Plain OM. And you too CNY. It good to have a starting point. I'll try and keep y'all posted.

 

[1 Lucky Texan]

what about the brake lights? do they come on when you step on the brake pedal?

maybe I'm thinking of a different problem.

 

[plain OM]

No, it's a good question. When the fuse for the stop lights blows, the shift lock will not release the gear lever from Park, which is one of the symptoms if I'm reading the previous posts correctly.

I don't know, however, if a blown stop light fuse would also affect the starting circuit, perhaps through the security system interrupt relay. I somewhat doubt it, but it's still worth checking the brake lights.