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Discussion Starter #1
About two weeks ago, my daughters 02 1.8T died on the road. When I arrived, I was able to start the car and drive it back to the house. I am an old air cooled guy with a 71 bus, so I tried to diagnose by component. I checked all fuses, replaced the fuel pump relay (aftermarket and then OEM), replaced the fuel pump (aftermarket), replace the driver’s door latch assembly (OEM), and replaced the engine speed sensor (OEM). Benny, my daughter’s name for her VW, will start, but will not run for more than three to four minutes. I purchased a code reader, not VAG-COM, and received the following codes:

P0725
P1780
P1850

I am at my wits end with the Snap Orange Demon sitting in the driveway. If anyone has any advice, I would greatly appreciate it. I have been searching forums for the last two weeks with little or no success. My next step is to purchase a VAG-COM to get more accurate diagnostics.

Brief History of what has been replaced over the last year:
Coil Packs – Dealer 6 months ago
Radiator – Me 3 months ago
Radio – Me Last Christmas (Had the dreaded parasitic amp draw, but was able to install relay. However, as of 3 months ago, there is no sound coming from the speakers. I’m not sure if this is related or not.) I could not convince my daughter that changing the radiator should have no effect on the radio/speakers
All Vacuum Hoses – Dealer one year ago

Have a day,
Rik
 

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Here you go a starting place. I would start with the crank position sensor. if you are going to continue to be the main mechanic on your daughters bug you need a good VW scan tool which will give live data. Search the threads here. There is a good one for about 40 bucks. The real good one( Ross Tech is about 400 but does everything). They have a lite version which works with some of the chinese cables for 99.

P0725 Volkswagen - Engine Speed Input Circuit Malfunction
Possible causes

- Faulty Crankshaft Position (CKP) Sensor
- Crankshaft Position (CKP) Sensor harness is open or shorted
- Crankshaft Position (CKP) Sensor circuit poor electrical connection
- Communication error between the Engine Control Module (ECM) and Transmission Control Module (TCM)

What does this mean?

When is the code detected?

The P0725 Codes is triggered when Transmission Control Module (TCM) does not receive the engine speed signal from Engine Control Module (ECM).

Possible symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

P0725 Volkswagen Description


The Engine Control Module (ECM) monitors the engine speed through the Crankshaft Position (CKP) sensor with the engine running, and send signal to the Transmission Control Module (TCM

Fault codes explanation:
P0725 = Engine speed input circuit; CAN-BUS no communication with Engine Control Module (ECM); Invalid data received from ECM; damaged ECM.
P1850 = Data-Bus Powertrain missing message from ECM.


I recommend you to access the ECM memory using VAG or similar diagnostic tool. But if you need to check a few things before scanning, I would recommend the following checks in your case:
- check the battery cables (clean and tight contacts)
- check engine ground cable (clean and tight contacts)
- check ECM (Engine Control Module) connectors and ground, the ECM is in plenum chamber under the windshield.
Having checked this wiring (most likely culprit), and made sure that contacts are clean tight, and connectors are fit, if the problem persists, (unlikely), you would need to get the codes using a VW equipment, to get the proper codes.
PS: there are some bulletins refering to ECM software updates on your model, so you should also check these out, if the problem points to ECM replacement eventually.

DTC P1850 is a serial data bus malfunction. Your computer network is not working properly. You need a scanner that can communicate on the ENTIRE computer network in your vehicle to find out the cause of these problems. Please note that a generic OBD code reader CANNOT perform this function. Volks Wagen is a whole breed of its own and requires special equipment and software to diagnose and repair.
 

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found another post about the same issue.
0725 is the engine speed sensor. Not sure if they mean the Vehicle speed sensor (tells the speedo how fast) or the crank position sensor. VSS makes more sense, it's on the transmission.

1780 is for park/neutral switch malfunction.

P1850 is for the TCM missing a message from the ECU. Check fuses, grounds, wiring, etc. This one here might be causing everything.
For more info:
18258/P1850 - Ross-Tech Wiki
 

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Discussion Starter #4
Thanks!

VDubYah,
I will continue to be the main mechanic on my daughter’s beetle. I cannot bring myself to pay for what I am capable of (most of the time) doing myself. There is just a learning curve for me when dealing with ECMs, TCMs, and VW scan tools. I'm sure I'll be beating my head against the wall for a few years.

I will purchase a good VW Scan Tool this weekend and also check all of the ground points. Actually, if I could leave the office right now, I would start checking ground points, so I’ll probably hit those tonight.

Thanks for your assistance and advice.
 

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Since you are going to continue to work on the car( funny how attached daughters get)If you do not have one I suggest getting a Bentley service manual. They are the official factory repair manual. Available as paper or electronic version. It does not give set by step directions like the aftermarket (Haynes, but has all of the factory specs and wiring diagrams and gives steps of what goes first etc.( reading them takes some effort but once you get the hang of how VW did them they make sense)

I would look at the speed senor after the grounds as that could be sending non-sense to the tcm and the ecm getting good info from the crank sensor causing codes

Good luck, once you get these cars figured out they really aren't to bad.
 

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Discussion Starter #6
VDubYah,

I located the ECM this morning. At one point, there was a mouse living in on top of the cabin air filter. I removed his nest and vacuumed all the leaves from both passenger and driver side. I removed the ground strap, cleaned and replaced. I also checked the ground strap under the battery tray. Tomorrow, I will continue checking grounds. However, today, the trunk decided it would not open with the FOB or the switch. I love this car.

Rik
 

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Discussion Starter #8 (Edited)
The saga continues

I have now cleaned the TCM ground points, the ECM ground points, and the main ground under the battery tray. I checked all of the fuses, one by one, and they are good. The fuses on top of the battery are also good.

Progress was made. The trunk now opens again. I'm not sure why it ever stopped. I was also able to get the radio working again. One of the wires leading into the relay (to fix the aftermarket battery parasitic drain) had come lose.

I have not been able to locate a VAGCOM I can borrow as of yet. I am still getting the same codes. My next step is to assume that there is a bad wire between the Speed Sensor and the ECM. However, it is raining and I do not feel like tracing wires in the rain.

Rik
 

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Discussion Starter #9
Troubleshooting Adventure

Here is my plan of attack based on some research from Fortitude.com. I am going to replace the 428 Relay under the hood. Based on what I have read, this relay supplies power to the ECU.

Current condition: Beetle starts. The RPMs at idle are roughly 1200 for one minute and then drop below 1000. After a few minutes, one of the following will happen: ECU light flashes, RPMs drop, but Beetle recovers and idles for two or three more minutes or ECU light flashes, engine dies, and the ASR/EDL light comes on.

Since I am on a mission to rebuild this car one piece at a time, I figure replacing the relays will not hurt. My local non-dealer VW mechanic charges $90.00 for diagnostic services. When we spoke, he said he would have to charge $90.00 an hour to trace the fault if it is electrical. I don't want to spend a few hundred dollars to find out I missed a ground or one of the relays was bad.

Have a day,
Rik
 

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Discussion Starter #10
Giving Up

I have decided to have the Beetle towed to my local non dealer VW specialist. However, after the repairs are made, I will post them on this site so others may use it as a reference. Thanks for Vdubya for the advice.
 

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Discussion Starter #11
Here is the final verdict.

The mechanic discovered the ignition wire was burned which ultimately fried the computer. He tried to find a used computer with the same box numbers, but nada. Unfortunatly, the only thing left to do is take it to the dealership and buy a new computer.

Have a day,
Rik
 

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Discussion Starter #13
The Saga Continues

Last Friday, I had Benny the Snap Orange Beetle towed to the stealership to have a new ECU installed. This afternoon, the stealership called and told me that their diagnostic software had been updated and they could not communicate with my daughter's 2002 beetle. I had little faith in the dealership in the first place, but I figured they would atleast try to get some money out of me. When I asked what I should do, they said I should purchase a new computer and have my mechanic install it.

Just for grins I called a dealership in Atlanta who assured me that it was possible to program the computer and he was not quite sure why my local VW Service Department could not accomplish this.

On another note, the salesman at my local dealership offered to sell me a new VW.
 

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Discussion Starter #14
Options

I have two options for getting Benny back on the road.

Option 1 - Used ECU with performance software Stage 1

Option 2 - New ECU with factory VW software

Option 1 could be done in town, while Option 2 requires towing Benny to Atlanta.

I would enjoy the performance software, but it is my daughter's car.

Any reccomendations?
 

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In all this saga, did the EPC code light come on along with the check engine light when it went down??? Mine has cost more than it is worth so far... it goes into "limpmode"?? and won't accelerate past 5-8 MPH... So far, I've had 02 sensors, MAF sensor, Throttle Body, hoses, Turbo dump gate valve, AND a new battery yesteday.... What next?
 

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I would go with the most cost effective.

Which I think is the used Stage 1.

The performance upgrade is amazing, it can be calm or it can be stomp on it fun. You will find yourself driving her bug more often.It's very street safe, unless you ask for it.

What brand stage 1?
 

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I would say if its your daughters car, stick with the stock tune ECU. Yes, the extra power is nice, but with a tune comes an increased chance for problems. A stock tune will get you longer term reliability.
 

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Discussion Starter #18
CalamityJ,

The EPC light came on each time the engine died. I am not sure if it is related to the issues. The check engine light is always on. When we purchased the car it had an after market cat converter. The stealership stated it would stay on until we replaced it with an OEM part.

The death of the ECU was the result of the ignition wire burning up. It was a slow process. It sounded like a relay clicking on an off while driving down the road. I replaced the turn signal relay twice thinking this is where the sound was coming from.

Johnny Ohio and Smileybug - Although I wanted the software upgrade, my wife pulled rank and we are going to get a new ECU with the factory software. She laughed when I read the two recommendations and stated that women are practical. However, when my daughter outgrows the beetle, I'm getting the performance upgrade.

Thanks to all who have offered advice over the past few months,
Rik
 

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The check engine light is always on. When we purchased the car it had an after market cat converter. The stealership stated it would stay on until we replaced it with an OEM part.
So what code(s) are still currently causing the SES/CEL/MIL to be on??

As for what the dealer said, this is total BS. My 2003 NBC 1.8t is on its 2nd replacement converter. Dealer replace the orignal under warranty for the P0420 code, not sure it was required. Then a large marble size chunk of the monolith broke off and was caught in between the 2 converter cells an rattled like crazy. I assume the replacement converter was dropped in shipping and handling??

So I replaced the dealer "replacement" converter with a $225 aftermarket converter about 15k miles ago and have NEVER had any problem or SES/CEL/MIL come on.

So the dealer is full of crap, unless there is a problem with the current replacement converter. But if the replacement converter is working properly, it should not cause any problems.
 

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Thank you, SJ's dad.... I hope you get yours going well again. Mine is my only driver now....we have diesel duallies for backup and farm use.... $$$$diesel!
 
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