Question Re Manual OBD Check
 

i have an intermittent problem with poor car performance that I would like to identify by
using a manual OBD check. By that I am referring to using a jumper wire across terminals
TE1 and E1 at the diagnostic port under the hood ('93SC400). I would like to keep the jumper
wire in place continuously until the problem shows up and then I can count the number of light
blinks to determine the code number.

My question is, can I leave the jumper wire in place without causing damage to the OBD system
or causing problems with normal car performance. I am concerned that if the jumper is not in place
when the problem pops up, I might miss the chance to get the readout because of losing the
"on engine light" on restart...i.e., engine light disappears and car runs normal again.

Hope this not too confusing.

See Erratic Performance thread by SC93 for details of my problem.

I don't see why it would hurt, but at the same time, I wouldn't leave it in place. I would assume the computer would store any codes and you can retrieve them once the check engine light comes on.

Can anyone else confirm or deny this?

Obd1 data storage
 

Thx for your reply.

OBD 1 will not store problem codes for subsequent retrieval.... OBD2 will store for retrieval. I have OBD1.

That is the basis for my question. I was having a problem which comes and goes. I was in one of those bad performance modes with engine light on When I drove up to my serviceman's garage, wouldn't you know, when I turned the ignition off and restarted the car, it started running normally. The engine light went off and he could not retrieve the the code number. The car may run normally for two weeks and then go into the poor performance mode.

My problem is described under thread "Erratic Performance" submitted by SC93 yesterday.

Unfortunately, ODB I is only for output, not input, as you stated. If you are able to catch the codes, you can indeed drive with the jumper still inserted. I would use a paper-clip, and if you still have the cover for the diagnostic, place it over carefully just to keep it from jolting in or out of place. I personally have driven about 20 miles no problem as I was encountering a similar problem. Definitely keep the speeds to a minimum, and "baby" the drive itself. ANd just in case you don't have it...

OBD1 Codes
1 Normal Condition.
2 Air Flow Meter signal.
3 Ignition signal.
4 Engine Coolant Temperature Sensor signal.
5 Oxygen Sensor.
6 RPM signal (Crank Angle Pulse).
7 Throttle Position Sensor signal.
8 Intake Air Temperature Sensor signal.
9 Vehicle Speed Sensor signal.
10 Starter signal.
11 Switch signal.
11 ECU/ECM.
12 Knock Control Sensor signal.
12 RPM signal.
13 Knock Control CPU (ECM).
13 RPM signal.
14 Turbocharger Pressure.
15 Ignition signal.
21 Oxygen Sensor.
22 Engine Coolant Temperature Sensor signal. 23 Intake Air Temperature Sensor signal.
24 Intake Air Temperature Sensor signal.
25 Air-Fuel Ratio Lean.
26 Air-Fuel Ratio Rich.
27 Sub Oxygen Sensor signal.
28 No. 2 Oxygen Sensor signal.
31 Air Flow Meter signal (Vacuum Sensor signal). 32 Air Flow Meter signal.
34 Turbocharger Pressure signal.
35 Turbocharger Pressure Sensor signal.
35 HAC Sensor signal.
41 Throttle Position Sensor signal.
42 Vehicle Speed Sensor signal.
43 Starter signal.
51 Switch signal.
52 Knock Sensor signal.
53 Knock Sensor signal.
54 Inter-cooler ECM signal.
71 EGR System.
72 Fuel Cut Solenoid signal.
78 Fuel Pump Control signal.
81 TCM Communication.
83 TCM Communication.
84 TCM Communication.
85 TCM Communication.

Good luck!

believe it or not odb1 will store the code as long as it is still occuring. the fact that when you restart it and its gone means its a running problem and not present when its started.

The solution is easy though, next time it happens, do not turn the car off. you can place the jumper in the diagnostic port with the car running. The cel will not have a chance to go off this way and you will be able to pull the code. If you are driving around with the jumper in all the time, you may not even get any new codes I am not sure anyone has tried that and I wouldn't because it will severly reduce your timing and not run as efficient at all.