average/instant/range indicators showing 0 in C4
Thread Starter
Racer
Joined: Oct 2002
Posts: 269
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From: Bigues Spain BCN
average/instant/range indicators showing 0 in C4
That is exactly what happens, the fuel range, average and instant fuel rate indicators in my 88 show 0 all the time, all other cluster functions work OK, even the fuel level indicator. Any ideas?
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Re: average/instant/range indicators showing 0 in C4 (JordiZR1)
The fuel mileage circuit in the cluster takes ECM injector pulse width and rpm and mileage info and calculates fuel mileage. So if the cluster isn't receiving any or all of this info, it can't calculate mileage. But, my guess is that circuit has a dead part and it needs to go to a cluster repair center.
Thread Starter
Racer
Joined: Oct 2002
Posts: 269
Likes: 0
From: Bigues Spain BCN
Re: average/instant/range indicators showing 0 in C4 (jfb)
Now I guess the problem is not with the cluster, it is intermitent (now it shows the data, now it doesn't), and when the range/mpg information dissapears from the cluster the engine hesitates and the idle goes from 600 rpm up to 1000-1100. Maybe the ecm is not getting the injector pulse?, what should I check?
:confused: :sad:
:confused: :sad:
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: average/instant/range indicators showing 0 in C4 (JordiZR1)
The ECM knows the injector pulse width as it establishes those.
It may not be getting the pulses from the speedometer signal from the tranny.
I have Gordon Killebrew's book on the digi-dash but it didn't cover this issue.
It may not be getting the pulses from the speedometer signal from the tranny.
I have Gordon Killebrew's book on the digi-dash but it didn't cover this issue.
Racer
Joined: Apr 2003
Posts: 426
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From: Detroit MI
Re: average/instant/range indicators showing 0 in C4 (JordiZR1)
This could also be the ECM as it sounds as if it is changing from one mode to another (600 then 1000 rpm idle). If you have scan tools check it when its fine and then when its not. Don't be suprised if you can't get data when the idle is at 1000 rpm you may be in limp home mode.
Team Owner
Joined: Mar 2000
Posts: 83,383
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From: Boston, MA
Re: average/instant/range indicators showing 0 in C4 (-js-)
Have you held down reset? I've seen this happen when the car is stuck in diagnostic mode before. If you unplug the 12V connector for the ECM for 1 minute you can force it to reset.
Thread Starter
Racer
Joined: Oct 2002
Posts: 269
Likes: 0
From: Bigues Spain BCN
Re: average/instant/range indicators showing 0 in C4 (scorp508)
I have an XRay code scanner but I have not checked for codes since I am not getting any SES light, but will check it tomorrow.
The speedometer works OK, so the ecm receives the speed signal correctly.
I will check the ecm-cluster connections and ecm grounds.
How does the ecm send all its signals to the cluster (I have never dissassembled it), a single connector or multiple connectors for every group of gauges?
The speedometer works OK, so the ecm receives the speed signal correctly.
I will check the ecm-cluster connections and ecm grounds.
How does the ecm send all its signals to the cluster (I have never dissassembled it), a single connector or multiple connectors for every group of gauges?
- 1986 Original Owner -
Joined: Apr 1999
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From: North Yorkshire, England
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Re: average/instant/range indicators showing 0 in C4 (65Z01)
I have Gordon Killebrew's book on the digi-dash but it didn't cover this issue.
There he says that the average/instant/range data comes from and is computed in the ECM and is passed to the CLUSTER for display.
The UPSHIFT signal also comes from the ECM and is sent to the CLUSTER for display. The CLUSTER sends FUEL LEVEL and MILES TRAVELED to the ECM. This is done on a bi-directional serial data line that runs between the ECM and CLUSTER. A tap from this line also goes to the ALDL for scanners.
Vehicle SPEED is also sent from the CLUSTER to the ECM but is done on a separate line. It is available from the ECM on the Serial Data Line.
[Modified by Ray Quayle, 10:15 AM 7/5/2003]
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