Hello!

It sounds like your computer is not grounded properly.

The check engine light should come on with the key in the on position.

I do not believe this is because of a fault prom.

CAUTION:
If the computer is found to be defective and needs replacement, remove the old PROM and place it into the replacement computer. Some ECM's are equipped with another chip called a CALPAK. If the computer is equipped with a CALPAK chip, it will be located next to the PROM and must be transferred along with the PROM. When replacing the computer always transfer the BROADCAST CODE and PRODUCTION ECM/PCM NUMBER to the service label on the replacement computer.

DESCRIPTION:
To allow one type of computer to be used for many different vehicles, a device called a Programable Read Only Memory (PROM) unit is used. The PROM is located inside the computer and has system calibration information based upon the vehicle's axle ratio, engine, transmission, weight, and other specific configurations of the vehicle.

Not sure if this applies to your vehicle or not, but I thought I would let you know.

Here is a tsb for an incorrect ecm installed from the factory.

90chevy22

Number: 90C19

Section: 6E

Date: May, 1990
Subject: PRODUCT EMISSION CAMPAIGN 90C19 INCORRECT ECM

Model and Year: 1990 G-VAN EQUIPPED WITH 5.7L ENGINE (LORDSTOWN BUILT ONLY)
General Motors has determined that certain 1990 Chevrolet G-Vans built at the Lordstown assembly plant may have been built with an incorrect ECM (Emission Control Module) installed.

To correct this condition, it will be necessary to install a new PROM in the ECM.

VEHICLES INVOLVED

Involved are certain 1990 Chevrolet G-Vans built at the Lordstown assembly plant within the following breakpoints:

MODEL YEAR PLANT FROM THROUGH

G-Van 1990 Lordstown L7100039

L7103442

Involved vehicles have been identified by Vehicle Identification Number Computer Listings. Computer listings contain the complete Vehicle Identification Number, owner name and address data, and are furnished to involved dealers with the campaign bulletin. Owner name and address data furnished will enable dealers to follow-up with owners involved in this campaign.

These listings may contain owner names and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this campaign. Any dealer not receiving a computer listing with the campaign bulletin has no involved vehicles currently assigned.

OWNER NOTIFICATION

Owners will be notified of this campaign on their vehicles by Chevrolet Motor Division (see copy of owner letter included with this bulletin).
DEALER CAMPAIGN RESPONSIBILITY

Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward.

Whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or it is in your dealership for service in the future, you should take the steps necessary to be sure the campaign correction has been made before reselling or releasing the vehicle.

Owners of vehicles recently sold from your new vehicle inventory are to be contacted by the dealer, and arrangements made to make the required correction according to instructions contained in this bulletin.

PARTS INFORMATION

Parts required to complete this campaign are to be obtained from General Motors Service Parts Operations (GMSPO). To ensure these parts will be obtained as soon as possible, they should be ordered from GMSPO on a "C.I.O." order with no special instruction code, but on an advise code (2).

Quantity/
Part Number Description Vehicle

16121134 Service PROM 1

SERVICE PROCEDURE

1. Referring to the Fuel and Emissions Service Information section of the 1990 Chevrolet Truck R/V, G, and P Model Service Manual (ST 330-90), pages 3-111 to 3-113, remove current PROM and install service PROM.

2. Install Campaign Identification Label.





CAMPAIGN IDENTIFICATION LABEL

Each vehicle corrected in accordance with the instructions outlined in this bulletin will require a "Campaign Identification Label." Each label provides a space to include the five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or a ball point pen.
Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner.

Apply "Campaign Identification Label" only on a clean, dry surface.





CLAIM INFORMATION

Submit a Product Campaign Claim with the information indicated below:
Dealers will automatically receive the correct labor and material allowance based on the labor operation performed.

Refer to the Chevrolet Claims Processing Manual for details on Product Campaign Claim Submission.
May 14, 1990

Dear Chevrolet Owner:

This notice is sent to inform you that Chevrolet Motor Division is conducting a recall campaign that includes your vehicle.

REASON FOR THIS RECALL

General Motors has determined that certain 1990 Chevrolet G-Vans built at the Lordstown assembly plant may have been built with an incorrect ECM (Emission Control Module) installed.

WHAT WE WILL DO

To correct this condition, it will be necessary to install a new PROM in the ECM.

WHAT YOU SHOULD DO

Please contact your Chevrolet dealer as soon as possible to arrange a service date. Instructions for making this correction have been sent to your dealer. Please ask your dealer if you wish to know how much time will be needed to schedule, process and repair your vehicle.

The enclosed owner reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary inspection/correction in the shortest possible time. If you have sold or traded your vehicle, please let us know by completing the postage paid reply card and returning it to us. Should your dealer not schedule a service date within a reasonable time, you should contact the Chevrolet Customer Assistance Center by calling 1-800-222-1020.

If your dealer and the Customer Assistance Center are unable to remedy this condition within a reasonable time, you may wish to advise the Environmental Protection Agency, at the following address: Director, Manufacturer's operations Division (EN-340F), United States Environmental Protection Agency, XXX X XXXXXX. S.W., Washington, D.C. 20460. To ensure your full protection under the emission warranty made applicable to your vehicle by Federal Law, and your right to participate in future recalls, it is recommended that you have your vehicle serviced as soon as possible. Failure to do so could legally be determined to be lack of proper maintenance of your vehicle. Also, your vehicle may fail a state or local emission inspection test if this recall work is not accomplished.

We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction with our products.

Here is a diagram.

 

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Ok...

we are getting close!

 

Right now, we do not need a scanner. I have a feeling that it wont be necessary right now because we wont even be able to communicate with the computer because the computer is not waking up.

 

I will tell you what I have according to my references.

 

We need to see power at A6, C16, and B1.

 

We need to have good grounds on A11, A12, D1 and D2.

 

Here is a pinout chart.

 

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Edited by AMEDEE on 11/7/2008 at 12:05 AM

YES!

DO all this testing with the harness plugged in and let me know the results!


power at A6, C16, and B1.

 

grounds on A11, A12, D1 and D2.

Well there we go! Pull that fuse out! I bet its bad!

We are missing two powers to the computer.

I take it you have checked all the other fuses?

DO you need a diagram for these two powers?

We are just going to have to trace the wiring issue down until we find out were we are loosing power if this is not our problem.

Edited by AMEDEE on 11/7/2008 at 5:59 PM

Here is a diagram.

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This would make sense. B1 and C16 are on the same circuit.

Are we sure we are on the right fuse? "ECBM B" fuse. its a 10 amp.

You could try powering up this circuit and see if the computer comes to life!

If the new fuse has 12 volts on both sides, and we are still getting no voltage to those two wires to the computer, we simply have a break or an open somewhere in the circuit.

You will hear all the relays click and the check engine light will come on if you have the key in the on position.

A voltage drop would be a better test.

Just set your voltmeter to DC voltage and put either lead on both places you are testing.

But for a correct voltage reading. You need to have voltage running through the circuit.

The voltmeter should read 0.00