Retrieving Diagnostic Codes: 1998 Fleetwood Discovery 5.9L Cummins/Freighliner

[WindsorE]

SITUATION: 1998 Discovery 5.9L Cummins has intermittent check engine light.

BACKGROUND: The issue can occur when idling (i.e., running engine at storage facility) but will come and go even when idling. The engine, at idle, does not rev or sputter, just has the light. The issue also occurs after highway travel and coming into town. When this happens, there is intermittent power loss while the light is illuminated such as stopping at a red light and then accelerating. Then, when the speed comes back up, it seems that the power loss is resolved and the check engine light goes off. There is no other gauge or indicator issues noted.

ANALYSIS: I cannot find a connection for diagnostic trouble codes, but I assume there must be something somewhere. Under the dash, there are two rocker switches (image attached). Neither one seems to do anything, but I think depressing the "Engine Check" switch may have reset the check engine light.

REQUEST:

1. Where can I find the port for diagnostics?
2. What is the function of the two rocker switches (image)?
3. Advice on where to begin troubleshooting this issue.

Thanks in advance!

[hermanmullins]

WindsorE,

The switch "Idle Inc/Dec" are to allow you to increase your idle speed for warm up. The other, for me "??".

Herman

[WindsorE]

Thank you for the reply. I assumed as much for the idle speed rocker, but it does not seem to function. The way my rig achieves the idle up for warm up is using the blinker switch integrated cruise control. I would prefer the rocker switch, myself, and relocate it, but I would imagine that may be difficult. Still, these two switches seem to be down there for a reason, but ???.

Thanks again!

[manholt]

Are the 2 switches even hooked up to anything? Can you remove them and see if they are wired? If they are, trace them out. I suspect a lose ground. I also think the check engine, would be a link to engine analysis. The other one is like Herman said.

Carl

[dickandlois]

WindsorE,

The switches You posted a picture of - do allow you to read the engine codes on the 5.9 Cummings Engine.

The Check engine light will flash the codes stored.

To Read engine codes on the Freightliner Chassis

(The code must be active. i.e. Still showing as a Check Engine or other fault

1. Shut the engine off.

2. Hold the Engine Check switch down. Located down by the steering column.

3. Turn the ignition key to on.

Both the Check Engine (yellow) and the Stop Engine (red) will come on

momentary. If no fault is active, both lights will come on and stay on.

4. The Fault Code will flash in the following sequence.

First, the Check Engine (Yellow) lamp will flash. Then the Stop Engine light will

flash the error number's in sequence. There will be a short one or two second

pause between each number. When the number has finished flashing, (in red), a

yellow light will appear again. The three digit code will repeat twice in the same

sequence.

The lights flash each fault code out two times before advancing to the next code.

To skip to the next fault code sooner, or back to the previous code, touch the

switch labeled Idle Increase/Decrease . This is a center off rocker switch located

next to the Engine Check switch. If only one fault is active, the same fault will

flash again.

Rich.

[hermanmullins]

Rich, I have none of what you just described but have a question that might help. In #2 "Hold the engine check switch down.". How long do you need to hold the switch after you turn the ignition key on?

Herman

[dickandlois]

Rich, I have none of what you just described but have a question that might help. In #2 "Hold the engine check switch down.". How long do you need to hold the switch after you turn the ignition key on?

Herman

Herman, You would hold the switch down until you have all the codes recorded / saved in the ECM. The Codes will repeat again and again as long as you hold down the key. The Idle speed key will go back one code,with each click so one can record them if needed..

OH, If you press the Idle speed switch - you can increasing the idle speed set point, but only to a max. RPM set in the ECM software or set the speed by using the throttle and pressing the cruse button as posted by the O.P.

Rich.

[five]

Call Cummins with the engine number.

[cmarq]

Rich has the correct info.

I retired from Cummins 12 years ago. When a fault or problem occurs a code is created and the check engine light indicates there is a problem but is drivable with caution and get it checked as soon as you can.

The red stop engine light indicates a serious problem and should be shut down as soon as it is safe to do so. If a problem occurs momentarily the light comes on and goes out, A fault code is created and is stored in the ecm. it is called an inactive code and can not be accessed by the switches. It has to be read with a diagnostic tool. If the check engine light stays on it is an active code and can be read using the switches.

All codes are stored in the ecm until cleared with a diagnostic tool. The code is a numerical numbers called sids(sub system identifier) and pids (parameter identifier) these give the tech the info as to which system maybe the problem and causes, If the check engine light comes on and off at different times it keeps a count of how many times it happens. Just clearing or erasing the codes will not solve a problem.