ECU codes & cures - nikki
Cavalier 1989 2L Auto Gives code 49 =High Battery Voltage above 17 Volts. Engine management light only comes on briefly but Error Code is logged in ECU What might be the possible cause?
My thanks in anticipation Nikki
ECU codes & cures - RichardW
Does the light come on regularly or only sparodically?

Sounds like the voltage regulator on the alternator might be faulty, or it's just a spurious fault. You need to measure the voltage across the battery with the engine running - it should be around 14.4V. You may need to monitor the voltage whilst driving the car around to see if the voltage spikes when the light comes on - if so then the voltage regulator is at fault. If not then there is some sort of wiring / ECU fault that is making it think the voltage is high.

ECU codes & cures - nikki
Re Cavalier 1989 Mk111 ECU code 49 It may be helpful to know that the max voltage that can be measured at the battery terminals with the engine at 3000 rpm is 14.45 Volts not over 17 Volts as suggested by Error Code 49.Just additional information for those Sherlock Holmes types out there! Once again the Engine Management Light only comes one for a very short time, it never stays on!
Bosch Motronic EMUnit - nikki
This Bosch type 0 261-200-161 GM part No GM 90 324 331 as fitted to a Cavalier 1989 MkIII gives an occasional Code Error No 49 which is listed as High Battery Voltage This has been checked at 14,45 Volts at high engine revs. Yet Code 49 suggests that the voltage should be over 17 Volts to produce this error.
The Engine Management light only stays on for a moment but the errors is logged into the Engine management contol unit. I have received one suggestion that it might be the Alternator-- or the Voltage regulator, which I don't appear to have, except for the instruments! For which many thanks-- But in truth the fault does not sem to be the battery, the alternator or the non existent voltage regulator.Does any one have other ideas or do I just wait until it becomes worse?
Regards NIKKI
Bosch Motronic EMUnit - SteveH42
You *will* have a regulator, no question. However, it may be built in to the alternator, or piggy-backed on it.

A transient problem may suggest a dodgy earth somewhere on the system.
Bosch Motronic EMUnit - Andrew Moorey (Tune-Up)
Not uncommon for the voltage regulator in the alternator to intermittently go AWOL which will trigger the em light and log that code. Usually (at night) the driver is aware of a momentary brightening of the lights which co-incides with the light coming on. New alternator time...

Happiness is a T70 at full chat!
Bosch Motronic EMUnit - nikki
The main object of this note is to thank Richard, Derych, Andrew, & Steve for their comments on this ECU & Codes problem, In fact I find that a sperious 18 to 20 Volts can exist as a spike which plugs the Code No 49 in to the ECU's memory. A replacement alternator is to be fitted which will hopefully solve the problem
Once again my thanks to you all Regards regards NIKKI
Bosch Motronic EMUnit - Deryck Tintagel
Check that the battery terminals are clean and tight - a loose battery terminal could cause a load dump (>40V) which could trigger the High Battery Voltage fault. Is there a specific fault code for load dump?
Bosch Motronic EMUnit - stator
Try the earth lead on alternator or try fitting additional earth lead direct from battery.
Bosch Motronic EMUnit - nikki
Many thanks for the suggestion about the alternator Earth Lead. The problem is now cured, it was the ALTERNATOR a replacement has been fited, All's Well!. My thanks to all 'This problem is now solved & closed' NIKKI

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