Service engine light not working

Hi Stevey818, Thank you for the donation. The is an onboard self-diagnostic system that you can use. Try it and see if you can come up with anything. SELF - DIAGNOSTIC SYSTEM NOTE: Electronic Control Module (ECM) and Powertrain Control Module (PCM) are same system; terms are often used interchangeably. Self -diagnostic system consists of 4 components. These components are Powertrain Control Module (PCM), Instrument Panel Cluster (IPC) options, A/C Programmer (ACP) options and Supplemental Inflatable Restraint (SIR) system. In addition to monitoring a particular set of sensors and switches, PCM maintains continuous communication with each system component. Should a component exceed pre-programmed limits, PCM will recognize a malfunction and may act to control malfunctioning component. To control a particular component, PCM rapidly switches an internal circuit between zero and 5 volts, converting programmed control information into series of pulses that represents coded serial data messages. These messages are transmitted to malfunctioning component, which interprets information and responds accordingly. As a result, an alphanumeric code, known as a trouble code, is often set in PCM memory. This trouble code identifies malfunctioning component and can be accessed by a service technician as an aid to diagnostic procedures. All trouble codes are displayed on Driver Information Center (DIC) panel. In addition to monitoring self -diagnostic system and displaying trouble codes, PCM can be programmed by service technician to perform specific diagnostic tests on individual components and systems. Results of these tests are displayed on DIC. This article covers accessing PCM trouble codes and programming self -diagnostic system to perform specific diagnostic tests on system components. ENTERING SELF - DIAGNOSTICS 1 . Turn ignition on. Simultaneously push OFF and WARMER buttons on Climate Control Panel (CCP). Continue pushing OFF and WARMER buttons until segment check appears (about 3 seconds) on Instrument Panel Control (IPC). NOTE: Failure of any segment to glow may result in inaccurate test results. Replace any inoperative segment display before proceeding with self-diagnostic process. 2 . When segment check appears (all segments glow), system has entered into self -diagnostic mode. Release both buttons. Driver Information Center (DIC) will display diagnostic codes. Diagnostic code level displays PCM codes first, followed by IPC, ACP and SIR codes (if so prompted). 3 . To proceed to desired level, press and release CCP panel HI (fan up) button for "yes" or LO (fan down) button for "no". Depress LO button to go to next test level (i.e., IPC?, ACP? or SIR?) or depress OFF button to return to next selection in previous test level. 4 . To exit diagnostics, press AUTO button on IPC. System will go back to normal vehicle operation. DISPLAYING TROUBLE CODES 1 . Diagnostic code level displays PCM codes first, followed by IPC, ACP and SIR codes (if so prompted). Trouble codes appear in ascending (3 -digit) numerical order and are prefixed by "P" (PCM), "I" (IPC), "A" (ACP) or "R". A final digit of either a "C" (current) or "H" (history)" will also be indicated on every code. 2 . For complete list of available PCM trouble codes, see PCM TROUBLE CODES table. If no codes are present for a system, a "NO X CODE" message (with X being system, i.e. "P", "I", etc.) will be displayed. If communication line to a component is not operating, a "NO X DATA" message will be displayed, indicating that IPC could not communicate with that system. 3 . To continue with system diagnostics, see SERVICE MODE OPERATION. To exit from SERVICE MODE and go back to normal vehicle operation, depress AUTO button on IPC. PCM TROUBLE CODE DEFINITIONS Code Test Condition P012 (1) No Distributor (TACH) Signal P013 (1) (5) Rear Oxygen Sensor Not Ready P014 (1) Shorted Coolant Sensor Signal P015 (1) Open Coolant Sensor Signal P016 (2) Alternator Voltage Out Of Range P017 (1) Front Oxygen Sensor Not Ready P019 (2) Shorted Fuel Pump Feedback Signal P020 (2) Open Fuel Pump Circuit P021 (1) Shorted TP Sensor Circuit (Signal Voltage High) P022 (1) Open TP Sensor Circuit (Signal Voltage Low) P023 (1) Ignition Control Circuit Problem P024 (1) (6) Vehicle Speed Sensor (VSS) Circuit Problem P025 (2) 24X Reference Signal Low P026 (1) Shorted Throttle Switch Circuit P027 (1) Open Throttle Switch Signal P028 (1) Transaxle Pressure Switch/Circuit Problem P029 (1) Transaxle Shift "B" Solenoid Problem P030 (1) ISC RPM Out Of Range P031 (1) Shorted MAP Sensor Circuit P032 (1) Open MAP Sensor Circuit P033 (2) Extended Travel Brake Switch Input Circuit Problem P034 (1) MAP Sensor Signal Too High P035 (3) Ignition Ground Voltage Out Of Range P036 (1) Exhaust Gas Recirculation (EGR) Valve Pintle Position Out Of Range P037 (1) Shorted Intake Air Temp (IAT) Sensor Signal P038 (1) Open Intake Air Temp (IAT) Sensor Signal P039 (1) (4) TCC Engagement Problem P040 (1) Open PSPS Circuit P041 (1) No CAM Sensor Signal P042 (1) (5) Front Oxygen Sensor Lean Signal P043 (1) (5) Front Oxygen Sensor Rich Signal P044 (1) (5) Rear Oxygen Sensor Lean Signal P045 (1) (5) Rear Oxygen Sensor Rich Signal P046 (1) Front-To-Rear Bank Fueling Imbalance P047 (1) IPC -To-PCM Data Problem P048 (1) EGR System Fault P051 (1) PROM Error P052 (3) PCM Memory Reset P053 (3) Distributor Signal Interrupt P055 (3) TP Sensor Out Of Range P056 (1) Transaxle Input Speed Sensor Circuit Problem P058 (3) Pass-Key Fuel Enable Problem P060 (3) Cruise Control With Transaxle Not In Drive P061 (3) Cruise Control Vent Solenoid Problem P062 (3) Cruise Control Vacuum Solenoid Problem P063 (3) Vehicle Speed & Set Speed Difference Too High P064 (3) Cruise Control Engaged/Acceleration Too High P065 (3) Cruise Control Servo Position Sensor Failure P066 (3) Engine RPM Too High With Cruise Engaged P067 (3) Set/Coast Or Resume/Accel Switch Shorted P068 (3) (6) Cruise Control Servo Position Out Of Range P069 (7) Traction Control Active While In Cruise P070 (3) Intermittent TP Sensor Signal P071 (3) Intermittent MAP Sensor Signal P073 (3) Intermittent Coolant Temp Sensor Signal P074 (3) Intermittent Intake Air Temp Sensor Signal P075 (3) VSS Signal Interrupt P076 (1) Transaxle Pressure Control Solenoid Circuit P080 (1) Fuel System Rich P081 (3) CAM To 4X Reference Correlation Problem P083 (1) 24X Reference Signal High P085 (1) Idle Throttle Angle Too High P086 (1) Undefined Gear Ratio P088 (1) Torque Converter Clutch (TCC) Not Disengaging P089 ( 8 ) Long Shift And Maximum Adapt P090 (2) TCC Brake Switch Input Problem P091 (2) Transaxle Range Switch Problem P092 (2) Heated Windshield Request Problem P093 (9) Traction Control System Pwm Link Failure P094 (1) Transaxle Shift 'A' Solenoid Problem P095 Engine Stall Or Near Stall Detected P096 (1) Torque Converter Overstress P097 (3) Park/Neutral - To-Drive/Reverse Shift At High Throttle Angle P098 (3) Park/Neutral - To-Drive/Reverse Shift While In ISC Control Range P099 (3) Cruise Servo Applied Not In Cruise P0102 (2) Shorted Brake Booster Vacuum (BBV) Sensor P0103 (2) Open Brake Booster Vacuum (BBV) Sensor P0105 (2) Brake Booster Vacuum (BBV) Too Low P0106 (9) Stop Lamp Switch Input Circuit Problem P0110 (10) Generator "L" Terminal Circuit Problem P0112 EEPROM Failure P0117 (1) Shift "A"/Shift "B" Solenoid Circuit Open Or Shorted P0131 Active Knock Sensor Failure P0132 (1) Knock Sensor Circuit Failure P0137 (11) Loss Of ABS/TCS Data (1) This fault turns on SERVICE ENGINE SOON light. (2) This fault turns on SERVICE VEHICLE SOON message. (3) This fault does not turn on any light or message. (4) This fault disengages TCC for ignition cycle. (5) This fault enables EVAP control solenoid. (6) This fault disables cruise control for ignition cycle. (7) PCM disables cruise control. ( 8 ) Code sets, no service telltale. (9) DIC message displayed "TRACTION DISABLED". (10) DIC message displayed "BATTERY NO CHARGE". (11) PCM sets all serial data from the Anti -Lock Brake Traction Control System to zero. STATUS LIGHTS DISPLAY Upon entering PCM system level of self -diagnostic mode, indicator lights on DIC automatically indicate operational status of TCC, certain emission control components and A/C compressor operation. Operational status of these components is indicated by corresponding status light being on or off.

NOTE: IPC, ACP and SIR systems can also be tested in SERVICE MODE. Only information related to PCM diagnosis is in this article. After PCM trouble codes have been displayed, SERVICE MODE can be used to exit diagnostics or individually perform other tests on different systems. Selecting System Level Following trouble code display, first available system will be displayed (i.e., IPC?). When selecting a system to test, any of following actions may be taken to control display: 1 . Depressing HI (fan up) button on CCP will select displayed system for testing (i.e., PCM DATA, PCM INPUTS, PCM OUTPUTS, etc.). 2 . Depressing LO (fan down) button on CCP will display next available system selection (i.e., IPC?, ACP? or SIR?). This allows display to be cycled through all system choices. This list of systems can be repeated following end of system list. 3 . Depressing OFF button on CCP will stop system selection process and return display to beginning of PCM trouble code sequence. Selecting Test Type Level Selection of PCM DATA, PCM INPUTS, PCM OUTPUTS, PCM OVERRIDES, PCM CLEAR CODES or PCM SNAPSHOT test may be displayed. If dashes appear in DIC, test is not valid or test conditions are wrong. While selecting a specific test, any of following actions may be taken to control display: 1 . Depressing HI (fan up) button on CCP will display a specific output or test parameter for selected test type level (i.e., PCM data parameter PD01, etc.). 2 . Depressing LO (fan down) button on CCP will display next test type level for system level (i.e., PCM INPUTS?, PCM OUTPUTS?, etc.). This allows display to be cycled through all available test type choices. This list of test types can be repeated following display of last test type. 3 . Depressing OFF button on CCP will stop test selection process and return display to next system level (i.e., IPC?). Selecting Clear Codes Selecting PCM CLEAR CODES test will result in PCM CODES CLEAR message being displayed with selected system name for 3 seconds, indicating all stored trouble codes have been erased from memory. After 3 seconds, display will automatically return to next available test type level (i.e., PCM SNAPSHOT?). After a code has been cleared, make a complete ignition cycle and possibly a test drive. Ensure code does not reset. PCM LOCATION PCM is located behind right side of dash, above kick panel.

Self-diags. showed P041, replaced cam sensor, SES light is now off when engine running but does not come on with other instrument lights in ignition on position. Gas mileage is a little better 9.7 up from 8,9 after driving 30 miles. I was expecting better mpg. I'll watch it for a few weeks and see what I get.

Innova tech support confirms Equus 3120 code scanner not compatible with 1993 Eldorado although manual says it is.

Did you clear the codes after replacement of the sensor?

Yes, codes have been cleared

My mechanic said he cleared the codes after replacing the CAM sensor. I took to another mechanic a few days later, (today 9/30) who checked with his scanner, no service engine light on. He showed me P052 and P109 on his scanner but they don't activate SES light. They show as history on self-diags. but he says they show on his scanner as current not history and I should get a new ECM. His scanner says P052 is "defective ECM, RAM chip error. P109 Internal ECM problem (KAM checksum). My mechanic says they are history and not causing a problem, the new mechanic says they are current and could be causing my gas mileage problem, stilll running rich, 9.2mpg. What to do, who's right?

Reset the ECM and clear the codes.

Drive around for a few days and get it scanned agaiin to see if the codes come back.

[quote:fce70263c8="KHLow2008"]Reset the ECM and clear the codes.

Drive around for a few days and get it scanned agaiin to see if the codes come back.[/quote:fce70263c8]


In my previous msg. I didn't understand that my regular mechanic had not completely cleared everything that was showing in the Self-diags. including history. I went back to the 2nd opinion mechanic who got the 2 ECM error codes and he did a complete clear including history, don't know if that included ECM reset, I will ask. He said drive for 5mi. and come back. I did he scanned and got no codes or history but his scanner says "right O2 sensor lean" and "left O2 sensor rich" no P codes, no SES light. Not sure why both these guys didn't see that in the first scans, I will ask them. They have been very patient with me and I them. I thought O2 sensors might have been the problem weeks ago but got no error codes. I have read that SES may not activate until O2 sensor is dead or beyond some threshold? In the meantime I will drive for a few days and get another scan.
Hate to be so long winded. I know most people don't like to wade thru long msgs. just throwing in some detail for anyone that can use it. hope it helps somebody. I'll keep it brief and concise from now on. I'm new to scanners and ECM/PCM error codes, etc.
Thanks for any and all input

Thank you for sharing your experience, it is appreciated.

It is ok to write a long message if it is to explain something. With a short msg, the info might be incomplete and that would defeat the purpose.

However from a technical view, I would prefer to go by point form as it is easier to present and understand.

Our database does not provide any info on using scanners as the vehicle has a self diagnostic system, which I have outlined earlier the procedures.

A lean or rich O2 sensor would trip the SES as indicated in the data.

After driving 70 miles for a week, mpg is 8.7, codes cleared, pcm reset. No error codes.

[quote="KHLow2008"]Thank you for sharing your experience, it is appreciated.

A lean or rich O2 sensor would trip the SES as indicated in the data.[/quot

After reading this:

"If the O2 sensor circuit opens, shorts or goes out of range, it may set a fault code and illuminate the Check Engine or Malfunction Indicator Lamp. If additional diagnosis reveals the sensor is defective, replacement is required. But many O2 sensors that are badly degraded continue to work well enough not to set a fault code, but not well enough to prevent an increase in emissions and fuel consumption. The absence of a fault code or warning lamp, therefore, does not mean the O2 sensor is functioning properly. The sensor may be lazy, or biased rich or lean."

I had the 2 front o2 sensors replaced but not the one on the catalytic converter. After driving about 20 miles in heavy city traffic I am now getting 15-16 mpg, up from a low of 8.2 mpg. 15 mpg in the city is the new EPA estimate for the 1993 Eldorado 4.6L. That's fine with me.

So you have managed to almost double up the mileage and got the vehicle to run as expected. Thank you for the input, it would definitely be of good help to others who might be facing the problem.

[quote:fef3badea2="KHLow2008"]

A lean or rich O2 sensor would trip the SES as indicated in the data.[/quote:fef3badea2]

After reading this :
https://www.2carpros.com/articles/how-an-oxygen-sensor-works

"many O2 sensors that are badly degraded continue to work well enough not to set a fault code, but not well enough to prevent an increase in emissions and fuel consumption. The absence of a fault code or warning lamp, therefore, does not mean the O2 sensor is functioning properly. The sensor may be lazy, or biased rich or lean."

I had the 2 front sensors replaced. After driving 20mi. in heavy city traffic.I now get 15-16mpg, 15mpg is the new EPA rating for 1993 Eldorado in city driving. That's fine with me.