OBD codes... What Am I Chasing? - Toyota FJ Cruiser Forum
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post #1 of 41 (permalink) Old 01-24-2019, 07:24 PM Thread Starter
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OBD codes... What Am I Chasing?

Last week, I installed OME struts, springs and shocks. Two drive cycles and I get a P0345 code - camshaft position sensor fault, bank 2. I switched the VVT sensors driver-to-passenger, cleared the code, and then got a P0340 code - camshaft position sensor fault - bank 1.

So I thought I was on it. I purchased and replaced the VVT sensor for (then) bank 1.

Two drive cycles and I now have a P0335 code - crankshaft position sensor circuit malfunction.

No driveability issues, starter seems fine, battery passes a load test.

Do I replace the crank position sensor, or is there something else going on?

Thoughts?

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post #2 of 41 (permalink) Old 01-25-2019, 03:24 PM Thread Starter
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Re: OBD codes... What Am I Chasing?

A decade and 106,000 miles for a first sensor failure, and twelve hours and 15 miles for a second. DO you think they are connected? Can a failure of a sensor CAUSE another failure?

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post #3 of 41 (permalink) Old 01-26-2019, 06:02 PM Thread Starter
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Re: OBD codes... What Am I Chasing?

Nobody?

It still seems odd that two sensors would fail so quickly.

I looked at a wiring diagram. If I read it correctly, the wires for the crank sensor, leaving the ECU are #21 black and #20 white, in connector C (B-3). I removed all of the connectors from the ECU, made sure they were clean and pins appearing straight. Cleared the code and it reset in a few miles. I figure the shop would replace the crank sensor before anything else, so off I go...

I removed the serpentine belt. Four bolts hold the AC compressor on, and they are fun to remove. First, the aftermarket skid plate had to be removed. Front top, front bottom and rear bottom bolts seemed best removed from the underside. Fortunately you can SEE them. Rear top bolt removed from engine access. Remove one bolt to allow the AC line to move around - this bolt was missing on my rig.

The bolt that holds the sensor is down in a depression, and so far I have not been able to loosen it from the top or the bottom. Best prospects seem to be from the bottom. I have been unable to move the AC compressor enough to SEE the bolt. I will tie the AC compressor back so I can maybe get my big, fat hands in there. The part is ordered, and I will likely give it another try tomorrow. This kind of work drives me nuts - so many obstacles, I can only see the area with one eye, which makes the depth perception difficult.

Let me know if you are interested in this, and I will post more.

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post #4 of 41 (permalink) Old 01-26-2019, 06:05 PM
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Re: OBD codes... What Am I Chasing?

Tell me more!

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post #5 of 41 (permalink) Old 01-26-2019, 06:20 PM Thread Starter
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Re: OBD codes... What Am I Chasing?

I was reading more about the P0335 code - "sensor circuit malfunction." Indications are that a lack of return signal can set the code, like with a dead sensor. As many codes as there are, I was worried that this specifically indicated a fault other than the sensor itself. Codes 336, 337, 338 etc also deal with bad sensor signals.

I thought the crank position was required for the engine to run. Apparently not true - the signal is used to refine the ignition timing but not vital.

I will try to extract that sensor tomorrow. New sensor should be here Monday afternoon. More wrench porn on the way!

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post #6 of 41 (permalink) Old 01-27-2019, 12:34 AM
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Re: OBD codes... What Am I Chasing?

Don't blindly replace parts hoping that you'll eventually stumble upon a fix - perform the required diagnostic work FIRST.

Using a quality digital multimeter, measure the crankshaft position sensor's DC resistance both hot and cold. Cold resistance should be 1,630 - 2,740 ohms; hot resistance 2,065 to 3,225 ohms.

The best check for the sensor is to monitor the pulse output with a lab oscilloscope. Pulse amplitude should be at least 1.5 volts (3V peak-to-peak), and there should be 34 pulses per engine revolution.

Then, check wiring continuity back to the ECM.

Here is a some info including a schematic and illustration showing the sensor output pulse shape and amplitude:
http://www.ezdries.net/Vidpics/4Runn...E)/cip0335.pdf

Last edited by FJtest; 01-27-2019 at 12:44 AM.
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post #7 of 41 (permalink) Old 01-27-2019, 01:13 AM
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Re: OBD codes... What Am I Chasing?

Sounds like a job for a properly equipped workshop.
I'd hate to replace a bunch of sensors just to discover that some earth wire is loose...

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post #8 of 41 (permalink) Old 01-27-2019, 06:59 AM Thread Starter
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Re: OBD codes... What Am I Chasing?

Quote:
FJtest previously said: View Post
Don't blindly replace parts hoping that you'll eventually stumble upon a fix - perform the required diagnostic work FIRST.

Using a quality digital multimeter, measure the crankshaft position sensor's DC resistance both hot and cold. Cold resistance should be 1,630 - 2,740 ohms; hot resistance 2,065 to 3,225 ohms.

The best check for the sensor is to monitor the pulse output with a lab oscilloscope. Pulse amplitude should be at least 1.5 volts (3V peak-to-peak), and there should be 34 pulses per engine revolution.

Then, check wiring continuity back to the ECM.

Here is a some info including a schematic and illustration showing the sensor output pulse shape and amplitude:
http://www.ezdries.net/Vidpics/4Runn...E)/cip0335.pdf
Good information! Thanks for providing that. The resistance test will be easy when I get the sensor out. I imagine that removal would be necessary to check the sensor independent of the wiring harness - the connector is behind the AC compressor.

I don't have a scope, so this question comes from curiosity. Where does one read that information? Does the scope access via the OBD2 connector or does a shop use a break-out box at the ECU? Or is the crank sensor self-powered by induction?

Amaclach, I like to give a repair a fair shot before I take it in. A combination of (maybe misplaced) pride, and the intersection of shop labor versus parts cost. I have been surprised at the good results from replacing the sensor that the code reader says is faulty.

The time will come soon-enough when I can't do this stuff any more.

Matt B
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post #9 of 41 (permalink) Old 01-27-2019, 08:43 AM
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Re: OBD codes... What Am I Chasing?

Quote:
oldMattB previously said: View Post
Good information! Thanks for providing that. The resistance test will be easy when I get the sensor out. I imagine that removal would be necessary to check the sensor independent of the wiring harness - the connector is behind the AC compressor.

I don't have a scope, so this question comes from curiosity. Where does one read that information? Does the scope access via the OBD2 connector or does a shop use a break-out box at the ECU? Or is the crank sensor self-powered by induction?

Amaclach, I like to give a repair a fair shot before I take it in. A combination of (maybe misplaced) pride, and the intersection of shop labor versus parts cost. I have been surprised at the good results from replacing the sensor that the code reader says is faulty.

The time will come soon-enough when I can't do this stuff any more.

Matt B
Check all the earth points anyway. You might be surprised :-)

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post #10 of 41 (permalink) Old 01-27-2019, 09:18 AM Thread Starter
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Re: OBD codes... What Am I Chasing?

Quote:
amaclach previously said: View Post
Check all the earth points anyway. You might be surprised :-)
I think I have identified the ground point for the crank sensor, and I will address it. Thanks for the reminder.

I have fixed many things by cleaning ground points. I bought a motorhome that had been sitting for years for repair and resale. Generator won't run? dirty ground. Bath fan won't come on? dirty ground. Dash gauges? dirty ground. Starter cranks slowly? dirty ground. etc!!

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