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740GL: many fuses have lost power!

The car will not accelerate past 20 MPH, I am sure it is because the ECM has lost power. Checked fuses with ign on, and car running. Fuse nos. 11, 25, and 17-22 have no power at all being supplied to them. These are all 15 amp. There didn't appear to be a common bus, but almost surely they are all powered from the same source to all be dead. I do not have a schematic for 89 model, Haynes only covers to

88 model, and I think it is different. Could someone with a correct schematic check and see wha tis likely to have opened? I figure it must be an ignition switch or a problem with one of the relays, perhaps one of them right behind the fuses. However, they are all seated, and wiggling/tapping them did not fix loss of 12v power to the fuses. The chk. engine light WAS onfor many days until the engine suddenly refused to accelerate. Probably a bad o2 sensor....but it's operationally off now, but still tests when switch is first turned on. That is why I think the ECM has lost power. Thanks!
Reply to
Geronimo
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should have stated it is a 1989 model. And I see from other posts here that there is another fuse box in the engine compartment, so I will try to locate that and see if one of those has popped.

Reply to
Geronimo

If the ECM loses power the engine won't run at all, it controls the fuel injectors.

Reply to
James Sweet

If the ECM lost power your car wouldn't start because the ECU grounds the fuel pumps through the FP relay.

You need a new air mass meter. The ECM is getting a 'bad' signal from the AMM and thus reverting to a closed loop 'limp home mode', which results in a super rich mixture and very little power. You might find that eventually the car will start and idle, but not accelerate at all.

Reply to
Scott

Reply to
John Robertson

YOu might be right. I was completely off-track with the observations about the fuses, I found out all of the fuses that were not getting power were for the lights..which were all turned off. (duh!!) However, shouldn't I have a check eng lite illuminated if the ECM is getting a "bad" signal from the AMM? It is not coming on now. But in the days just prior to the car going down for loss of acceleration, the lite was steady on. Then it ran perfectly, but was sure eating gas. As a test to see if the chk engine lite was still working operationally, I pulled the EMM conn. off, started car, and I got a chk eng lite right away. Might try pulling the o2 sensor conn. and verify that brings it on, too. It doesn't make sense....I have a bad sensor, but the ECM is not sensing it, as shown by the chk engine lite being on? I am sure a new AMM would cost a lot...is there any way to check it , like back-probing its output siginal with a DMM? Is there something else that could cause something like a "limp-home" condition. The car never stalls, but it just "chokes" when I hit the accelerator.Its limited to first gear, runs perfectly in park or neutral. Thanks for the help!

On Fri, 17 Jun 2005 12:44:01 GMT, "Scott" wrote:

Reply to
Geronimo

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