Gary RV_Wizard
Site Team
If there is a danger of engine damage, the Stop Engine light will come on, not Service Engine Soon. The light means what it says, that service is required "soon", but not immediately.
Service Engine Soon light
- Thread starter Bill N
- Start date
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OP
OP
Bill N
Well-known member
Basically the book says if the SES light comes on steady, then the problem is nothing immediate but if the light blinks you should make immediate tracks to a wrench bender.
Charlie 5320
Well-known member
Gary, how many gas rigs have you seen with a STOP engine light? I've never seen one.Gary RV Roamer said:
OP
OP
Bill N
Well-known member
Update on an old topic: The service engine soon light came on frequently (about every 100-150 miles) during our recent 2000 mile trip. I erased it each time with my OBDII gadget but I am pretty sure that the Knock Sensor 1, low input reading is bad. If it was the wiring, I don't think it would clear. Anyway, I have scheduled the knock sensor to be replaced and also to have all the roof seals checked by a good RV mechanic in our area. No known problem with the roof seals and the coach is always stored under cover but it never hurts to do routine maintenance on a 12 year old coach and I am one who gets dizzy at minimum heights so why not have a professional do the job. By the way, the old coach ran perfectly (other than the SES light) for the whole trip and every system on it worked as designed. While at the Winnebago Grand National Rally I watched the parade of much newer coaches going to the service center each day. They had 23 bays and 115 techs working so they could handle that large workload.
Gary RV_Wizard
Site Team
Sorry - I didn't notice this question until just now.
Answer: It will either have such a light, or it will slow or stop on its own if damage is imminent. As far as I know, every modern computer-controlled gas and diesel engine has the smarts to do that. What light or message the vehicle manufacturer chooses to display on the dash board is a different question. May not be the words "Stop Engine", but will be similar. My 2007 GM car starts sounding alarms and flashing the dash lights when things get serious and then enters a "limp home" mode if things get worse. My diesel coach has the words Stop Engine" on a display and a warning chime to call attention. It also begins to derate the power when that happens, but gives me a chance to get off the road or limp on.
JFR
Well-known member
There is a part of the engine and transmission electronic control system called the Diagnostic Executive.
It's job is to check parameters and decide when a series of checks is to be done. The MIL illuminates when these checks fail a given set of specs. That is why you can not expect the fault codes to return immediately. If the DE has decided the parameters have not been met it will not do the test. Case in point the fuel cap issue on 97 and new vehicles some later in larger chassis is checking the evaporative emissions system by applying a vacuum to the fuel tank if the tank is 1/4 to 3/4 full. The DE will not check it outside of those specs and so it will not fail a failing condition during a recent fuel fill up or while driving with less than 1/4 tank. Also with the engine running while filling up and the DE finds the parameters right to check evap emissions the check engine light will light because the DE is using engine vacuum to draw vacuum condition in the fuel tank (gas engines only)
The DE is the main reason check engine lights are much harder to diagnose. To add to the problem there are two set of codes the OBDII codes which are part of the EPA clean air act laws and proprietary codes which are more detailed in nature but do not show up on generic scan tools. The term Diagnostic Executive is a GM term but may have become universal.
Last point the more factory specific the diagnostic information is the more accurate the diagnosis becomes. Flow charts are used because sometimes the code indicates the circuit of a certain component not necessarily the component itself. Automobile technician are now using lab scope to test component on a regular basis. The scan tool is NOT immediate information it scans the circuit when is gets to it, this is known as sweep/refresh rate.
The people that due this everyday are very sharp and they earn their pay. Unfortunately, not every technician with a wrench and rag are trained the same.
Sorry about being so long winded.
JFR
It's job is to check parameters and decide when a series of checks is to be done. The MIL illuminates when these checks fail a given set of specs. That is why you can not expect the fault codes to return immediately. If the DE has decided the parameters have not been met it will not do the test. Case in point the fuel cap issue on 97 and new vehicles some later in larger chassis is checking the evaporative emissions system by applying a vacuum to the fuel tank if the tank is 1/4 to 3/4 full. The DE will not check it outside of those specs and so it will not fail a failing condition during a recent fuel fill up or while driving with less than 1/4 tank. Also with the engine running while filling up and the DE finds the parameters right to check evap emissions the check engine light will light because the DE is using engine vacuum to draw vacuum condition in the fuel tank (gas engines only)
The DE is the main reason check engine lights are much harder to diagnose. To add to the problem there are two set of codes the OBDII codes which are part of the EPA clean air act laws and proprietary codes which are more detailed in nature but do not show up on generic scan tools. The term Diagnostic Executive is a GM term but may have become universal.
Last point the more factory specific the diagnostic information is the more accurate the diagnosis becomes. Flow charts are used because sometimes the code indicates the circuit of a certain component not necessarily the component itself. Automobile technician are now using lab scope to test component on a regular basis. The scan tool is NOT immediate information it scans the circuit when is gets to it, this is known as sweep/refresh rate.
The people that due this everyday are very sharp and they earn their pay. Unfortunately, not every technician with a wrench and rag are trained the same.
Sorry about being so long winded.
JFR
