Q and A: Traction warning light not to be ignored
QUESTION: We have a 2006 Pontiac Grand Prix with 38,500 miles. Out of the blue, the "Service ABS" and "Service Traction" warning lights came on. I did check fuses and disconnected the battery for 30 minutes -- someone told me that would reset the...
QUESTION: We have a 2006 Pontiac Grand Prix with 38,500 miles. Out of the blue, the "Service ABS" and "Service Traction" warning lights came on. I did check fuses and disconnected the battery for 30 minutes -- someone told me that would reset the computer -- but the problems are still there. Is it safe to drive? The brakes seem to work just fine.
ANSWER: It may be safe to drive, but head to the dealer or shop right away. The warning lights indicate the ABS or traction-control systems have been disabled due to some type of problem. Disconnecting the battery will reboot the vehicle's computer, but the warning lights will re-illuminate if the issue is still there.
If the warning lights stay on after the initial self test, the most likely cause is a loss of "communication" with one of the ABS wheel speed sensors. If the warning lights go off after the self test and then come back on when you drive or apply the brakes, there may be a more serious issue.
Your next step is to have a shop connect a scan tool and read any fault codes stored in the computer. This will pinpoint the precise problem with the ABS or traction-control systems.
Q: I have issues with the idle speed at start-up on my 2007 Toyota Solara. When started cold, it idles at about 1,600 rpm. It takes several minutes for it to slowly idle down to 900 rpm when warm. I believe this is too high, especially in winter when the oil is thicker. Two Toyota dealers say this is normal. Do you agree?
A: The initial start-up idle "flare" of 1,600 rpm is certainly in the normal range. Carmakers have programmed engine management systems to idle up at start-up to heat up the catalytic converter as quickly as possible. This allows the system to shift "open loop" operation with a richer air/fuel mixture for starting and warm up to "closed loop" air/fuel mixtures trimmed by feedback from the oxygen sensor. This significantly reduces emissions and increases fuel economy.
With that said, Toyota specifies 630 to 730 rpm in neutral at idle after warmup, which is measurably lower than you indicate.
It's difficult to say whether this is normal in extremely cold temperatures or if there could be something like a vacuum leak affecting idle speed.
Q: I have a 2004 Jeep Grand Cherokee 4.7L V8 HO with 125,000 miles. Last winter on occasion when I would start the car after it sat all night there would be no oil pressure -- the gauge would not move at all and the "check gauges" light would be on. I immediately turned off the Jeep for fear that there was no oil circulating through the engine. I checked the oil level and it was always within the normal range. I ended up starting and shutting off the Jeep from three to 10 times until it showed normal oil pressure. The problem went away over this past summer but has returned now that the temperature has dropped below 40 degrees again. Any ideas?
A: Almost certainly this is an electrical issue. The only mechanical possibility would be moisture/ice in the oil pan preventing the oil pickup tube from drawing oil up into the oil pump. If this were a serious loss-of-oil-pressure issue, the engine would have failed by now.
The oil pressure sensor, on the left front of the engine, sends a signal to the PCM (powertrain control module), which sends a signal to the instrument cluster circuit board which operates the gauge. Check connections and grounds in this circuit -- that's where the problem is likely hiding.