2000 S70 ETM/MAF diagnostics

[Caberguy]

Thanks. I'll follow through on the voltage issue. In the mean time I have some interesting (I think...maybe) results from live data recording.

Based on what I've read, it seems unlikely that this is resulting from a vacuum leak, as my short term fuel trim is trending negative and doesn't change appreciably between idle and load.

In record mode, my reader seems to record a "frame" every second or two, here are the readings from a number of consecutive frames during an episode (edited slightly for brevity) cruising at low highway speeds (around 99kph as you can see), still reading no codes and no lights. I've highlighted a couple things that stand out to me... though, obviously, I'm still new at this. IAT, ECT, Fuel System status and DTCs were unchanged, so I omitted them.

In red I've highlighted where the absolute throttle position seems to fluctuate quite a bit from one frame to the next without any perceived change in input from my right foot. As I was driving I felt a definite surge/hesitation, looked down and noted the frame range where it occurred, these are the data that I found when I pulled over and reviewed them. The MAF readings parallel these spikes, though it's not clear to me if this is a result of the throttle opening suddenly and sucking more air, or if the throttle is responding to faulty MAF data. The spike and recovery of the MAF readings are highlighted in green.

In blue I've highlighted what seems like a fairly rapid spike in Intake MAP (connected, no doubt, to the above issues).

In yellow I've highlighted when the downstream o2 sensor reads higher than the upstream sensor, which strikes me as problematic, but what do i know.

Troubling load percentages are in brown and they seem to be all over the place too... dropping off strongly from 53% to 43% in the frame immediately before the MAF and Throttle position spike, and then jumping to 63% in the frame after the MAF/Throttle spike, and peaking at 67% a frame later.


Calculated Load Value(%)53.7
Short Term Fuel Trim -Bank 1(%)-2.3
Long Term Fuel Trim - Bank 1(%)-1.6
Intake Manifold Absolute Pressure(kPa)58.0
Engine RPM(rpm) 2184
Vehicle Speed Sensor(km/h)99
Ignition Timing Advanece for #1 Cylinder(¡£)33.0
Air Flow Rate from Mass Air Flow Sensor(g/s)21.69
Absolute Throttle Position(%)25.5
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.485
Short Term Fuel Trim Bank 1-Sensor 1(%)-3.1
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.730
Short Term Fuel Trim Bank 1-Sensor 2(%)-0.8
----------------------
Calculated Load Value(%)51.4
Short Term Fuel Trim -Bank 1(%)-5.5
Long Term Fuel Trim - Bank 1(%)-2.3
Intake Manifold Absolute Pressure(kPa)73.0
Engine RPM(rpm) 2184
Vehicle Speed Sensor(km/h)99
Ignition Timing Advanece for #1 Cylinder(¡£)37.5
Air Flow Rate from Mass Air Flow Sensor(g/s)18.42
Absolute Throttle Position(%)19.2
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.485
Short Term Fuel Trim Bank 1-Sensor 1(%)-7.0
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.765
Short Term Fuel Trim Bank 1-Sensor 2(%)-0.8
----------------------
Calculated Load Value(%)53.3
Short Term Fuel Trim -Bank 1(%)-9.4
Long Term Fuel Trim - Bank 1(%)-2.3
Intake Manifold Absolute Pressure(kPa)55.0
Engine RPM(rpm) 2151
Vehicle Speed Sensor(km/h)98
Ignition Timing Advanece for #1 Cylinder(¡£)34.0
Air Flow Rate from Mass Air Flow Sensor(g/s)19.32
Absolute Throttle Position(%)27.5
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.470
Short Term Fuel Trim Bank 1-Sensor 1(%)-8.6
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.230
Short Term Fuel Trim Bank 1-Sensor 2(%)-0.8
----------------------
Calculated Load Value(%)43.5
Short Term Fuel Trim -Bank 1(%)-5.5
Long Term Fuel Trim - Bank 1(%)-1.6
Intake Manifold Absolute Pressure(kPa)52.0
Engine RPM(rpm) 2141
Vehicle Speed Sensor(km/h)97
Ignition Timing Advanece for #1 Cylinder(¡£)34.0
Air Flow Rate from Mass Air Flow Sensor(g/s)18.00
Absolute Throttle Position(%)25.1
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.405
Short Term Fuel Trim Bank 1-Sensor 1(%)-7.0
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.125
Short Term Fuel Trim Bank 1-Sensor 2(%)-0.8
----------------------
Calculated Load Value(%)52.9
Short Term Fuel Trim -Bank 1(%)-6.3
Long Term Fuel Trim - Bank 1(%)-1.6
Intake Manifold Absolute Pressure(kPa)55.0
Engine RPM(rpm) 2144
Vehicle Speed Sensor(km/h)97
Ignition Timing Advanece for #1 Cylinder(¡£)33.0
Air Flow Rate from Mass Air Flow Sensor(g/s)31.93
Absolute Throttle Position(%)38.4
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.495
Short Term Fuel Trim Bank 1-Sensor 1(%)-6.3
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.135
Short Term Fuel Trim Bank 1-Sensor 2(%)-0.8
----------------------
Calculated Load Value(%)63.9
Engine Coolant Temperature(¡£C)92
Short Term Fuel Trim -Bank 1(%)-8.6
Long Term Fuel Trim - Bank 1(%)-2.3
Intake Manifold Absolute Pressure(kPa)60.0
Engine RPM(rpm) 2129
Vehicle Speed Sensor(km/h)96
Ignition Timing Advanece for #1 Cylinder(¡£)32.5
Air Flow Rate from Mass Air Flow Sensor(g/s)21.47
Absolute Throttle Position(%)17.6
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.470
Short Term Fuel Trim Bank 1-Sensor 1(%)-7.8
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.155
Short Term Fuel Trim Bank 1-Sensor 2(%)-1.6
----------------------
Calculated Load Value(%)67.1
Short Term Fuel Trim -Bank 1(%)-3.9
Long Term Fuel Trim - Bank 1(%)-2.3
Intake Manifold Absolute Pressure(kPa)70.0
Engine RPM(rpm) 2119
Vehicle Speed Sensor(km/h)96
Ignition Timing Advanece for #1 Cylinder(¡£)26.5
Air Flow Rate from Mass Air Flow Sensor(g/s)27.34
Absolute Throttle Position(%)31.8
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.480
Short Term Fuel Trim Bank 1-Sensor 1(%)0.0
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.680
Short Term Fuel Trim Bank 1-Sensor 2(%)-0.8
----------------------
Calculated Load Value(%)65.5
Engine Coolant Temperature(¡£C)92
Short Term Fuel Trim -Bank 1(%)0.0
Long Term Fuel Trim - Bank 1(%)-2.3
Intake Manifold Absolute Pressure(kPa)72.0
Engine RPM(rpm) 2133
Vehicle Speed Sensor(km/h)96
Ignition Timing Advanece for #1 Cylinder(¡£)27.0
Air Flow Rate from Mass Air Flow Sensor(g/s)27.65
Absolute Throttle Position(%)32.2
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.485
Short Term Fuel Trim Bank 1-Sensor 1(%)-0.8
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.655
Short Term Fuel Trim Bank 1-Sensor 2(%)-0.8


Again, I'm new at this, thanks for your patience and help. I'm definitely getting frustrated, and would rather not break down and take it to the shop. I really don't have the money at the moment, though I do have another vehicle, so I'm not dependent on the Volvo at the moment.

[Caberguy]

I know this is getting overwhelming. Just one more thing for the moment.

As I mentioned in my second post, the Xemodex ETM flow chart tells you to bridge fuse #2 with the negative battery terminal and measure the voltage. I did that and found that it was equal to the battery voltage.

Xemodex says this means that "There is an open circuit within power
supply wire (green/white) from
fuse#2 to pin #6 on the connector
plug. To remedy the problem either
open up engine harness and locate
the crimped wire splice close to the
fuse box, or run your own wire
between the fuse and the plug."

Any thoughts on that? Could that be the cause of both the vimpiric power loss and the weird readings. Suggestions on hunting it down?

[abscate]

Sounds like a bad ETM if it is spuriously reporting throttle plate changes, either real or imagined

You might want to check Dons ETM room, aka Room 101 for 1984 model Volvos

It's near the bottom of the Board index link


https://www.matthewsvolvosite.com/forums ... m.php?f=12

[Caberguy]

I've pretty thoroughly read through the various ETM chronicles scattered around the web. Some of my confusion is based on the fact that I'm only displaying some of the symptoms outlined here: https://www.matthewsvolvosite.com/forums/viewtopic.php?f=12&t=17252

For example, since I cleaned the ETM, it hasn't dropped noticeably below normal idle when coming to a stop, nor does it seem to be hunting at idle. Nor have I had any ETM related DTCs or ever experienced limp home mode.

Though, today, I did feel the "gust of wind" hesitation for the first time. I disconnected the MAF and drove for a while (this threw both the P0113 (Intake Air Temperature Sensor 1 Circuit High) and P0102 (Mass or Volume Air Flow A Circuit Low that I previously reported). Previously when there were incidents it felt more like surging, maybe the different systems were trying to compensate for each other. Today, though, there was a clear sensation of hesitation. I also found, with the MAF still disconnected, that there was distinct surging at lower speeds, and the sensation on a couple of occasions when setting off from a stop, that the car was just taking off on it's own, the brief unexpected acceleration actually made me nervous a couple of times in traffic.

As I reported yesterday, live data reporting showed fluctuations of up to 15-20% in throttle position between frames, I didn't manage to catch any data on the strong surges from a standstill.

I think I'll email Xemodex and see what they have to say about some of these things... hopefully they don't give me the hard sell.

[precopster]

Have you cleaned the MAF as yet? Denso MAFS are expensive to buy however I would gladly buy a used one due to the rarity of failure. Varying throttle plate positions are calculated by airflow AND TPS positions when using a generic scanner. Only Vida/Dice will provide accurate throttle positions because there are 2 sensors.

Given the symptoms and no ETM codes this would be my first suspect.

[Caberguy]

Just got back from the store with some MAF cleaner, I'll be under the hood again in the morning.

[Caberguy]

Cleaning the MAF didn't seem to have any effect. The bucking/hesitation when setting off came back again today, this is a new symptom over the last couple of days. It also seems to be idling more roughly over the last couple of days. It's been very humid with fog and a lot of rain.

[Caberguy]

I think I'm getting to the end of what I can do without starting to throw money at it. I'll dig more into the electrical system later this afternoon... unless it rains again.

This morning it passed the "glove test" for the PCV system.

I was able to reproduce the P1612 code by disconnecting the ETM, so it seems that all the codes I've had have been the result of my tinkering with it.

I've read that disconnecting the MAF can be a useful diagnostic tool, that if the MAF is causing the fault, that disconnecting it should improve the symptoms. I've also read some folks that disagree with that. Having disconnected the MAF with no improvement, and now having cleaned it with no improvement, am I correct in dismissing the MAF as a likely culprit?

Any brilliant ideas?

[Caberguy]

Battery tested ok, alternator tested ok. The battery was a little bit low again this morning. I know that there are some systems still active when the car is parked, blinky red light, etc. So obviously there's going to be some drain. What's normal?

The car has always started up straight away.

[precopster]

Leaky injectors, and failing coil packs can produce these symptoms. With a failing coil pack, usually the car will buck for afew days before it finally diagnoses itself and will be more noticeable when the engine is cold/damp.

With the MAF proper diagnostics are to have the kg/hr rate read at idle speed and should be around 14-16 without great fluctuations.

I haven't road tested a faulty ETM yer that didn't illuminate the ETS light on my Denso car.

In this case although MAF failure is rare this would be my first stop. A failing MAF on a Denso car isn't as easily diagnosed as just unplugging it.