My 1990 Caravan work van failed one aspect of the emission control test. Hydrocarbons and CO tests were very good but NitrousOxide failed. Causes, they suggest, might be lean fuel mix, EGR valve or catalytic converter. Engine control error codes show 12 23 and 42. How would you proceed?
PS It's a 3.0 FI engine here.
12: Start of codes 23: Air charge temperature sender improper value 42: ASD and/or fuel pump relay circuit (Z1) fault
Your "very good" HC and CO combined with high NOx suggests you're running lean, which could indeed be caused by the two faults your computer is squawking about.
"Daniel J. Stern" wrote: > On Wed, 18 May 2005, Awelch wrote: > > > My 1990 Caravan work van failed one aspect of the emission > control test. > > Hydrocarbons and CO tests were very good but NitrousOxide > failed. > > Causes, they suggest, might be lean fuel mix, EGR valve or > catalytic > > converter. Engine control error codes show 12 23 and 42. > > 12: Start of codes > 23: Air charge temperature sender improper value > 42: ASD and/or fuel pump relay circuit (Z1) fault > > Your "very good" HC and CO combined with high NOx suggests > you're running > lean, which could indeed be caused by the two faults your > computer is > squawking about.
Just took my ?88 Caravan for the emission test and it failed as well for the same reason. HC and CO were fine but the NO was the reason for the fail (1156ppm limit was 979ppm). I?m gonna pull the codes (if there are any) later tonight. I might just fix the EGR and get it re-tested...don?t really want to change the CAT unless I really have to.
"vp17" wrote: > Just took my '88 Caravan for the emission test and it failed > as well for the same reason. HC and CO were fine but the NO > was the reason for the fail (1156ppm limit was 979ppm). I'm > gonna pull the codes (if there are any) later tonight. I might > just fix the EGR and get it re-tested...don't really want to > change the CAT unless I really have to.
Had no error codes on the caravan. I?m just going to test and change the EGR if it isn?t working properly according to the Haynes manual.
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