1.Intermittent CEL light seemingly triggered by roundabouts and/or wet weather 2. Mechanics could not reproduce 3. Codes PO300 and Po303 4. Could feel the misfires


  1. Heard some small noises from engine
  2. Power steering on hard down sounded like the wheel was scraping a curb
  3. Rapidily deterioated
  4. Mechanic replaced steering pump.
  5. Now much looser with some noise on hard down. (Previously stalled on hard down, since new).

CONCERN 1. CEL now permanently on 2. Mechanic found no misfires on road test

QUESTION 1. Could the CEL and power steering be comnnected. Car is regularly maintained and has done 45000 miles. 2. What can I do to diagonse the CEL light and fix it?


  • Concerning the misfire, what has your mechanic checked? Was compression OK? Was the primary ignition circuit OK? What about the valve train? Was vacuum OK? Carbon on the plugs? Intake valves? Any technical service bulletins? – Ben Mar 6 '17 at 23:53
  • Thanks all - I am going to take it back in next week and they will go over it again. He believes it is not fuel related .. – jobucks Mar 9 '17 at 17:11

If I googled your car correctly, it has hydraulic power steering and not electric power steering. Hydraulic power steering does not have electronic parts, and thus, there is no warning light for it.

Even for electric power steering systems, there is generally a separate power steering warning light. The reasons for this are many:

  • More warning lights help to pinpoint the subsystem of the car that is malfunctioning before taking it to the mechanic
  • Electric power steering malfunctioning is in general more dangerous than engine malfunctioning. If the engine is malfunctioning, the worst that could happen is that your car lacks power when you need it and perhaps need to stop. If the power steering is malfunctioning, the worst case scenario is that it turns violently to the left (assuming traffic on the right side of the road) and you end up in front of the oncoming traffic. Obviously, engineers do everything they can to prevent this scenario, but if the power steering is malfunctioning, it is easy to understand it's more dangerous than engine malfunctioning. So, the power steering warning light is red like the oil pressure light (meaning stop driving the car now!) and the engine warning light is yellow (meaning you can continue driving the car, but you should repair the car soon) like the tire pressure light on cars that have TPMS.

Because of the reasons, even in electric power steering systems there is a separate warning light, and power steering issues will not light up the check engine light.

The proper fix for your CEL is to read the codes using an OBD reader. Most likely, you'll find that the code is related to the engine and associated components, not to the power steering system.

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  • 1
    hydraulic systems do use a pressure switch to inform the ecm that it should bump up the idle. – Ben Mar 6 '17 at 16:03
  • Ben - the light would come on while I was driving - so fifth gear, come up to a roundabout (my town is famous for them and has few traffic lights). I thought I was being lazy and not changing right down to second, one generally cruise through in 3rd or 4th. Wld that have triggered the CEL initially? And would different demands on the steering now 'encourage' the CEL to stay on? Should I ask for that pressure switch to be checked? The codes are PO300 and PO303 - random misfire, and the on cylinder 3 (presumably that time)? – jobucks Mar 6 '17 at 16:38
  • @jobucks I doubt the switch is bad, they rarely fail and they throw a separate code. – Ben Mar 6 '17 at 23:48
  • Thanks again! So two unconnected problems. Steering fixed by replacing the pump. Still to figure out the light – jobucks Mar 7 '17 at 12:54

By the way, ultimately, the mechanics found a faulty censor that was not only triggering the light but creating havoc with the emissions and causing misfiring.

All fixed now.

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