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Lil bastard · 10-31-2008, 07:47 AM

There are two types of P1128/30 codes. Above Limit and Below Limit.

Above Limit means that the A/F is running so lean - at idle, that the DME cannot richen it sufficiently with the maps it contains. Below Limit is the opposite, meaning that the A/f is so rich - at idle, that the DME cannot properly lean it out.

Here's what the DME 7.2 diagnostic manual says about P1128 (and 1130):

Above Limit:

P1128/P1130 - Fuel/air mixture so lean that sensing has reached its rich threshold.

Possible causes:

– Incorrect signal from MAF sensor
– Intake air system leaking
– Fuel pressure too low
– Volume supply of fuel pump too low
– Fuel injectors fouled
– Exhaust system leaking

Below Limit:

P1128/P1130 Fuel/air mixture is so rich that sensing is up to its lean threshold.

Possible causes:

– Incorrect signal from MAF sensor
– Fuel pressure too high
– Fuel injector leaking
– EVAP canister purge valve open

Note:

If DTC P0445 (EVAP canister purge valve – short to ground) is stored in the memory, correct this fault first. An open EVAP canister purge valve can lead to the lean threshold being reached. Contrary adaptation values in connection with misfiring point to adjusted control times - check control times and adjust if necessary. If the fuel tank reserve light is switched on, no fault is entered.

There are values for tests of the various components mentioned. If you want these, PM me with an email and I can get them to you.

10-31-2008, 07:47 AM	#3
Lil bastard Registered User Join Date: Feb 2008 Location: Du Monde Posts: 2,199	There are two types of P1128/30 codes. Above Limit and Below Limit. Above Limit means that the A/F is running so lean - at idle, that the DME cannot richen it sufficiently with the maps it contains. Below Limit is the opposite, meaning that the A/f is so rich - at idle, that the DME cannot properly lean it out. Here's what the DME 7.2 diagnostic manual says about P1128 (and 1130): Above Limit: P1128/P1130 - Fuel/air mixture so lean that sensing has reached its rich threshold. Possible causes: – Incorrect signal from MAF sensor – Intake air system leaking – Fuel pressure too low – Volume supply of fuel pump too low – Fuel injectors fouled – Exhaust system leaking Below Limit: P1128/P1130 Fuel/air mixture is so rich that sensing is up to its lean threshold. Possible causes: – Incorrect signal from MAF sensor – Fuel pressure too high – Fuel injector leaking – EVAP canister purge valve open Note: If DTC P0445 (EVAP canister purge valve – short to ground) is stored in the memory, correct this fault first. An open EVAP canister purge valve can lead to the lean threshold being reached. Contrary adaptation values in connection with misfiring point to adjusted control times - check control times and adjust if necessary. If the fuel tank reserve light is switched on, no fault is entered. There are values for tests of the various components mentioned. If you want these, PM me with an email and I can get them to you. __________________ 1990 Porsche 964 Carrera 4 Cabriolet 1976 BMW 2002 1990 BMW 325is 1999 Porsche Boxster (gone, but not forgotten) http://i933.photobucket.com/albums/a...smiley-003.gif Never drive faster than your Guardian Angel can fly!