Help,interior lights don't come on when you open the doors, but work with the switch. Door locks and everything else works fine. Some module some place? Also I get "sys" three times in a row on the speedo?

Help!!

 

The flashing SYS is due to either a battery that's going south or an aftermarket stereo install. My '90 had been doing the flashing SYS for a couple months, the battery was going south and final will no longer hold a charge...I had a stereo installed a couple years ago and had no flashing SYS, when the SYS started I was told the stereo was the culprit but it made no sense that it was fine prior to parking my car and need a jump to start it.

The interior lights problem my be a simple switch stuck closed.

Good luck!

 

Both doors or just one door?

The SYS lamp flashes 3 times every 15 seconds if there is a problem with a CCM controlled component. Are you familiar with pulling the codes?

 

I took it to a friend of mine that works for a Caddy dealer and he put a scanner on it and it din't have any codes in it.

 

sorry both doors

 

both switches are ok!

 

I do not know about a 90 vette, but my 87 had the interior light time delay relay go south (It failed open). It caused the same problem with the interior lights. There are ways to jump it out so the lights work with the door switchesI do not think the system light is related.

 

Here's a image of the DLC connector, the pin outs and button function labels.




The Diagnostic System functions are 1.x for CCM, 4.x for ECM, and 9.x for ABS/ASR. The primary one's to know are x.1 to display DTCs and x.7 to clear the codes. So for example 1.1 displays CCM DTCs and 1.7 clears CCM DTCs.


- By jumping with a paper clip A to G you can put the system into CCM Diagnostics mode.

- Turn the key On.

- You select the display data function by repeatedly presing the TRIP/ODO button until 1.1 is shown on the trip monitor.

- Then press the ENG/MET button until the first DTC (Diagnostic Test Code) is displayed. Continue pressing the ENG/MET button to display additional CCM DTCs until the end of information --- appears. If a C12 appears that indicates no stored DTCs for the CCM.

Write down the codes if any. They will be: 12, 13, 14, 16, 21, 22, 24, 25, 26, 27, 31, 32, 33, 34, 35, 36, 37, 38, 41, 51, 52, 53, 54, 61, 62 or 63. Definitions of each if necessary can be given. But that's what your looking for there. The other two diagnostics ECM and ABS/ASR are slightly different.

 

pulled codes tonight, got "H25 and H41. 25 is "courtesy lamp circuit open" NOW WHAT?

 

Yep Courtesy Lamp Relay Coil Circuit Open or Shorted to Ground. the 41 is ECM loss of serial data. Probably one caused the other. The H means they are historical codes.

You can direct the output of the CCM to cycle On and Off. This is very helpful in determining if certain portions of a circuit or component are in working order.

Repeat the procedure to enabled CCM diagnostics, except cycle the TRIP/ODO until 1.4 is shown in the trip monitor area of the cluster. Then, press the ENG/MET button until 10 is shown in the first two digits of the odometer. If it is necessary to go backwards use the FUEL INFO button.
The status of the output being cycled is shown as a "0" OFF or "1" ON in the last digit of the odometer. The output status cycles between ON and OFF every three seconds.
Cycling the output to the courstesy lamp relay (10 above) can indicate whether the circuitry from the CCM to the relay, the relay itself, and the circuitry from the relay to the bulbs are good. If, for example when cycling the output to the courtesy lamp relay, the relay is heard to be clicking and the I/P output indicator is cycling from 0 to 1 to 0, but the bulbs are not lighting when the display indicates 1 ON, there is a good possibility that the problem lies in the wiring from the relay to the bulbs. In the same instance, if the relay were not cycling, it could be the wiring from the CCM to the relay, the relay, or in very rare instances the CCM.

Run this test to isolate where the problem lies.

Next phase if the problem is not identified, you'll need a test lamp.

 

Thanks, That's Tomorrow Nights Task!

 

Well, I checked it out tonight, the relay does not "click"

 

Ok you've isolated it down to the relay or the wiring from the CCM to the relay.

The relays are located behind the knee panel on the passenger side. If you need details to access, identify and test the relay I'll post it tomorrow. The testing requires a test light so if you don't have one stop by home depot or radio shack type place and pick up a 12 v lamp. Should be under $5.00.

 

I have a test light and will wait for your post.
P.s. what do you fly?besides the Vette

 

Don't feel bad I also have a problem with my interior lights working off and on...

I've checked the door switches and they both work but I still don't have interior lights. Every once and a while I'll open a door and they will flash or come one for a few seconds then go out. Makes no sense to me.

I narrowed it down but don't know where to look next. When the lights don't work I found that both wires to the bulbs are hot. When they do work I have one hot and one ground.

 

OK let's see if we can get you going so you can resolve this issue. Based on what was isolated so far it appears to me to be the relay or wiring from relay to CCM.

Let's run a few diagnostics:

First you'll need to remove the RH Trim panel so you can get access to the relays.

- Remove the fuse box cover.

- Remove the IP side trim panel RH. Should be two torex screws.

- Remove the screws mounting the lower trim panel to the support and IP (Instrument Panel is what they call the whole panel not just in front of the driver.) There is carpet on the side it is held on with velcro pull it away and there are screws underneath. Also the screws along the bottom. Disconnect the courtesy lamp harness.

Remove the Courtesy Light Relay. (There are five relays there. Starting from the radio console working towards the door they are in a group of two and group of three. And are Fog Lamp relay, Courtesy Lamp Relay, Fuel Pump #1 relay, Horn relay, and Rear Defog relay.)

Connect a test light between terminal 86 of the relay connector and ground. Do the lamp light?

No: you have an open or short to B+ n CKT 740. Also check the RH CTSY fuse.

Yes: Connect the test light between treminals 87 and 86 of the relay connector. Do they light?

No: Repair open in ground CKT 150 (G202)

Yes: Connect the test light between terminals 85 and 86 of the relay connector. Do they light?

Yes: Check for an open in CKT 156 between relay connector and splice S232. If ok, replace courtesy lamp relay.

No: Connect the test lamp between term C12 at the CCM gray connector and B+. Open the driver's door. Do the light?

No: check for open in CKT 745 or ground CKT 150 to LH Door Ajar switch. If ok, replace LH door ajar switch.

Yes: connect the test light between terminal D16 at the same CCM gray connector and B+. Open the passenger door. Do they light?

No: Check for open in CKT 746 or ground CKT 150 to RH Door Ajar switch. If ok, replace RH Door Ajar switch.

Yes: Check for open or short to B+ in CKT 690. If Ok, perform the ambient light sensor functional check.

Lets see what some of the results you get on the first few steps. Then if need be I'll detail the ckt and or get you a image of the schmatic.

The courtesy lamp relay connector is a 5-way F Metripack series. the pin ut is

2
1 3 4
5

To help orient a white wire comes into terminal 30, orange wire to terminal 86, black wire to terminal 87 and gray to terminal 85.

I hope this is enough to isolate. Let me know I'll check back going to wash the Vette.

 

DAMN, HE'S GOOD!!!

Care to help me next?

 

I'd be happy to but not that familiar with the 85. Of course you can try to follow up to this point if yours is similiar in this instance.

 

I tried in the begining but it appears to be very differant. I just recieved the under dash wiring diagram for my 85 from another forum member (Much thanks!) and it looks like I have a Diode Module that controls my interior lights. I'm wondering if I have a bad solder connection on that board. I think that would probobly be the best place to start.

Your thoughts?

 

Well guess what??? With no relay you get no lights or no "click" with a relay you get "click" and LIGHTS!!!!!!! But without your help I was lost. Ordered a service manual today.

thanks again!