95 XLT intermitent check engine light - I have the codes :)

[EmilioD]

Hey all,
This is my first post, but I have been reading this forum for some time now. Its great the wealth of knowledge and the help that is here.

I have a 1995 XLT that came from Florida last year. I have had no major problems with it at all, so far. It sat idle in a snow drift for 3 months after it came up to NY. I got it 2 months ago, and it running / legal again.
Occasionally, after the engine has warmed up the check engine light comes on, not often (maybe 1-3 times a week) and even goes off sometimes.
This weekend the weather was warm enough for me to try the KOEO and KOER tests I have read about here. The engine appears to be running fine and smoothly. Here are the results of the tests. I would like to know what they mean as well as what to do.


Key on Engine Off Codes
Fast Codes
335 - EGR feedback signal is/was out of range - EVR or PFE
Pause
1 pulse
Pause
117 - ECT sensor is/was low or grounded - ECT
327 -EGR feedback signal is/was low - EVR or PFE
332 - EGR did not open/respond during test or if memory code, did not open intermittantly - EVR or PFE (Memory code thing)

Engine On Test without Goose Test
111 or 3 - System Pass or 6 cylinder
Engine does some tests
326 -Pressure Feedback EGR shows low pressure EGR not seating or not seating intermittantly - PFE
538 - System did not receive "goose" test - TESTS - NONE PERFORMED so not a problem
536 - Brake On Off open or shorted to ground - BOO- NOT SURE ABOUT THIS ONE, I NEVER PRESSED THE BRAKE
632 - E4OD - Transmission Control Switch (TCS) should be cycled once between engine ID and Goose test

Engine On Test with Goose Test
111 or 3 - System pass or 6 cylinder
Engine does some tests
one pulse for goose
"Goose the engine” when the check engine light flickers, I release the throttle
326 -Pressure Feedback EGR shows low pressure EGR not seating or not seating intermittently - PFE
536 - Brake On Off open or shorted to ground - BOO- NOT SURE ABOUT THIS ONE, I NEVER PRESSED THE BRAKE
632 - E4OD - Transmission Control Switch (TCS) should be cycled once between engine ID and Goose test

The only difference with/without goose test is 538 indicating i didn't do the goose test on that cycle.

I don’t know a ton about the ins and outs of engines but I am very familiar with electronics and sensors. From what I can tell the problem is with the exhaust gas recirculation (EGR), as I understand it, a valve system that uses exhaust to raise the combustion temperature?
Do I need to get this looked at / fixed soon?
Can I fix it?
What will the truck do/not do if it doesn’t get fixed?

Thanks, and I really look forward to reading your responses.

 

[cjones101812]

117 - ECT was the engine fully warmed up??

538 didn't do the snap test
536 didn't press the brakes
632 didn't cycle the Overdrive button

the 327, 332, and 335 is what you should look at.

327 is normally a bad DPFE. do a search for code 327 and you should see a number of threads on it.

but you should also check for cracks and blockage of the rubber hoses that attach to the DPFE sensor (code 335).

 

[EmilioD]

well it is kinda cold here (about 25F) but yes the engine was warmed up, I drove about 20 minutes before doing the test. I will look into the DPFE Sensor. Thanks alot for the quick response.

 

[MrShorty]

SOP when resolving codes is to focus on the KOEO codes (what you referred to as "fast codes" in your list). Because KOEO codes are set while the engine is off, they almost always represent electrical faults.

So your KOEO code is a 335, which, as noted, points to a fault in the DPFE sensor circuit. I'd probably start by getting a wiring diagram (even the one in Chiltons should be adequate) and testing the DPFE sensor circuit. If the wiring between the PCM and the DPFE checks out, then replace the DPFE sensor. Then clear CM and see what happens.

As for the KOER test: you figured out the "goose" test, now you just need to remember to press the brake and cycle the OD off switch after engine id is output. You might review my notes on pulling EEC-IV codes thread.

 

[EmilioD]

I will take a look at the DPFE circuit and then replace the sensor.
The fast codes that I was referring to are almost like the light is flickering, as you described in your notes. Is there someway to read those codes?

Is there a better wiring diagram than Chiltons, if so which do you recommend?

 

[cjones101812]

117 ECT below min voltage 254* F indicated.

disconnect ECT sensor (remember it's the 2wire sensor) and clear and rerun the codes. is 113 or 118 now present?? if so, bad sensor.

you can pickup inexpensive code readers from most auto parts stores.

before replacing the DPFE run the checks i gave for 94xlt earlier this month

1. clear the codes. key OFF.
disconnect DPFE sensor connector.
jumper the connector at the BR/LG and BR/W terminals on harness.
did code 337 appear??
if code 337 appeared replace DPFE sensor.
if not, remove jumper, Key ON Engine OFF and measure VREF (BR/W) at sensor connector.

 

[MrShorty]

The fast codes that I was referring to are almost like the light is flickering, as you described in your notes. Is there someway to read those codes?

I'm sure there is a way, but I don't know what it is. I've heard a couple of different descriptions of what's in the fast codes: either it's the same information as comes out in the "slow" codes, or it's information used at the point of manufacture that isn't needed later. Since I've never seen any diagnostic information that says, "this comes exclusively from the fast codes" I have never worried about trying to read them.

 

[cjones101812]

this may clarify types of codes:

Computers and Control Systems: Reading and Clearing Diagnostic Trouble Codes Reading Self-Test Service Codes

PURPOSE
The Electronic Engine Control (EEC) system communicates service through the self test codes. These codes are three digit numbers representing the results of the self test.

OPERATION
The Diagnostic Trouble Codes (DTC) are transmitted on the Self Test Output (STO) wire located on the vehicle self test connector. The codes are in the form of timed pulses, and are read by the technician using a scan tool, Analog Volt/Ohm Meter (VOM) or by monitoring the CHECK ENGINE light.

TYPES OF DIAGNOSTIC TROUBLE CODES

Fast Codes
Fast codes are given prior to regular DTCs. These codes contain the identical information as the regular DTCs but are transmitted at 100 times the normal rate. These codes are used at the factory and by scan tools. If a VOM is used to retrieve codes the fast codes should be ignored. Some VOMs in service may detect these fast codes as a short burst (meter deflection).

Hard Codes
The hard (on-demand) codes are displayed in both the Key On Engine Off (KOEO) and Key On Engine Running (KOER) self tests. If a hard code is displayed it means that there is a fault present in the system at the time the test was run. In the KOEO self test, the hard codes are displayed first. The hard codes are the codes up to, but not including the separator code (10). In the KOER self test the hard codes are the last codes displayed and will follow the "goose" code.

Dynamic
The dynamic response (goose) code is displayed during the KOER test only. It is displayed as single pulse (10 on a scanner) and is displayed after the engine ID code. When the "goose" code is displayed, the operator should briefly go to wide open throttle. This input is used to test the operation of the Throttle Position sensor, Mass Air Flow sensor, Manifold Absolute Pressure sensor, and Knock Sensor.

Separator
A single 1/2 second separator pulse is issued 6-9 seconds after the last functional test code (KOEO only). Then 6-9 seconds after the single 1/2 second separator pulse, the continuous codes will be issued.

Continuous
The continuous codes are issued as a result of information stored (memory codes) during continuous self-test, while the vehicle was in normal operation. These codes must be retrieved within 80 (40 on some models) warm-up cycles. On the 81st (41st on some models) warm-up cycle these codes will be erased. These codes can be manually erased during the KOEO self test. These codes are displayed only during the KOEO testing after the separator code.

Engine Identification Codes
Engine identification codes are issued at the beginning of the Key On Engine Running test and are one-digit numbers represented by the number of pulses sent out. The engine ID code is equal to 1/2 the number of engine cylinders (i.e. 2 pulses = 4 cylinders). These codes are used to verify the proper Powertrain Control Module (PCM) is installed and that the self-test has been entered.


NOTE: All trouble codes should be diagnosed in the order they are received.

 

[EmilioD]

ok, so in summery,
Try disconnecting the ect sensor, if I get 113 or 118 then the ECT sensor is bad. If no change then disconnect or short the DPFE Sensor and look for code 337, which if present indicates a bad DPFE sensor, and should be replaced.

is that all correct?

just curious, what are the effects of a bad DPFE sensor, does the engine run rich because of incomplete combustion or what? is there a loss of power? I haven't really noticed any thing different driving it daily to work. other than the CE light comes on.

Thanks again for all the help. Ill run these check as soon as I can.

 

[cjones101812]

almost,

Try disconnecting the ect sensor, if I get 113 or 118 then the ECT sensor is bad. If no change then

we continue with that (code 117) flow chart.

disconnect or short the DPFE Sensor and look for code 337, which if present indicates a bad DPFE sensor, and should be replaced.

correct, (disconnect and short the DPFE connector) but if you don't get a 337 then we continue with the code 327 flow chart.

just curious, what are the effects of a bad DPFE sensor, does the engine run rich because of incomplete combustion or what? is there a loss of power? I haven't really noticed any thing different driving it daily to work. other than the CE light comes on.

i have never come across a drivability concern because of it. you'd normally see a problem when running an emissions test. the ECM uses that sensor to calculate the optimum amount of EGR flow.