HOW-TO: TPS Tester/ECU Code Light

Phoenix7 · 04-03-2008, 06:38 PM

Thanks to TeamFC3S for the info.

To build the tester you will need the following parts (or equivalents) available from Radio-Shack:

2 units of Red LED Lamp Assembly, Cat. No. 276-011a. These are red LED's that looks like regular 12V lamp indicators and can be mounted in a 21/64 (8.3mm) diameter hold.
2 units of Male Quick Disconnects (10), Cat. No. 64-3038a. Each of these bags contain 10 assorted spades, among them 4 non-isolated and 2 isolated 0.25" spades. We highly recommend to use isolated spades to prevent short circuit between the spades when connecting them to the Diagnostic Connector. This is why you need two units to have the three 0.25" spades we need for the tester.

Figure 1. Parts needed

These components are pretty standard and compatible ones are available from various sources. If you can't get them from Radio-Shack, try any automotive store for the spades and an electronic supplier for the LED assemblies (Digikey might be a good candidate, and their full catalog is available on-line). If you can't get a LED assembly with built-in current limiting resistor, you can build them them from scratch as described in the diagram below. The resistor can be of any value from 330 to 1000 ohm. We recommend to use a 510 ohm resistor that will result in current of about 20 ma through the LED. The diode is used to protect the LED from reverse voltage in case the tester is connected improperly. Any diode such as 1N4001 with a breakdown voltage of 25V or more and maximal current of 100 ma or more will protect the LED just fine.

Figure 2. LED Schematics with Reverse Voltage protection

The construction of the tester is very simple, just follow these two easy steps:

Connect together the two anodes to a spade (use a crimping tool if you have one) . This will be ABR lead.
Connect each of the cathodes to a spade. These leads will be DCC1 and DCC2 respectively.

Figure 3. Completed Tester.

To check the tester, connect the ABR lead to the (+) post of the battery and connect the DCC1 lead to ground. Make sure that the DCC1 LED lit. Repeat the step for the DCC2 lead. If the test was OK, you are ready to test it using the ECU itself. First turn the ignition switch OFF. Then insert the three spades of the tester to the ABR, DCC1 and DCC2 pins of the diagnostic connector. Make sure you connected the right spades to the right pins. Turn the ignition switch ON (you don't have to actually start the engine) and watch the two LED's. They should be on for about 3 seconds and then will go off. If any error code exists, one or two of the LED's will periodically flash. The next section contains a detailed description of how to interpret the flashes and determine what the error codes are.

Phoenix7 · 04-03-2008, 08:19 PM

Once you finish building the tester you need to test it and make sure it's working properly:

To check the tester, connect the ABR lead to the (+) post of the battery and connect the DCC1 lead to ground. Make sure that the DCC1 LED lit. Repeat the step for the DCC2 lead. If the test was OK, you are ready to test it using the ECU itself. First turn the ignition switch OFF. Then insert the three spades of the tester to the ABR, DCC1 and DCC2 pins of the diagnostic connector. Make sure you connected the right spades to the right pins. Turn the ignition switch ON (you don't have to actually start the engine) and watch the two LED's. They should be on for about 3 seconds and then will go off. If any error code exists, one or two of the LED's will periodically flash. The next section contains a detailed description of how to interpret the flashes and determine what the error codes are.

Figure 4. The light connected and about to be used.

The DCC1, DCC2, and GL signals (Figure 6) are 'open collector' digital outputs of the ECU. The ABR signal is a switched +12V power of the Air Bypass Relay and is used as the +12V supply for the DCC. The DCC1 and DCC2 signals are used to read the error code. The signal GL is used to test/adjust of the Closed Loop System and is not used for the error-code reading procedure described here. The DCC1, DCC2, and GL signals are binary and can be in one of two states: LOW where the voltage is close to 0V and HIGH where the voltage is close to +12V. However, since these outputs are 'open-collector' they require a 'pull-up' to +12V to have high voltage in the HIGH state. This pull-up can be for example a 1K Ohm resistor connected between the signal and the ABR. However, if you are using the LED based monitoring circuit described later, you don't need to connect a pull-up resistor since the LED and its serial resistor provide the pull-up.

NOTE: The ECU seems to protects its output by limiting to 30 ma the current its DCC1, DCC2 and GL output sinks. It is strongly recommended however not to rely on this fact and to use a load that will not require more than 20-30ma. The ECU is essential for proper operation of the engine and is pretty expensive so you cannot be too careful in protecting it.

For the purpose of reading the error codes, monitoring the signals means observing the HIGH/LOW states of the DCC1 and DCC2 signals. When the ignition switch is turned on, the two signals are LOW for about 3 seconds and then they change to HIGH (provided a proper pull-up is connected). If an error code exists, the ECU generate bursts of LOW pulses on DCC1 and/or DCC2 that uniquely identify the error code (this is described in details later). The duration of the pulses are 400 ms or higher and therefore they can be monitored using a simple binary indicator and a human eye, assuming that the indicator has fast enough response. To monitor these pulses, we use a simple tester with two LED indicators, one for DCC1 and one for DCC2.

There are connectors next to the coil between the driver's side wheel well and battery and ou're supposed to use the 6-pin connector:

Figure 5. ECU connector pins for ECU code checking

Figure 6. Which pins to use for the ECU codes.

Phoenix7 · 04-03-2008, 08:45 PM

The codes are displayed with a sort of Morse code. There are short (1/2 second) flashes of light which correspond to a count of 1 and long (2 seconds) flashes which correspond to a 5. These pulses are counted until the long pause (2 seconds) that indicates the end of the code. DCC1 indicates the one's digit of the error code and DCC2 indicates the ten's digit. DCC1 will flash either short or long pulses. Because of the limited number of two-digit codes (12 and 15) DCC2 will only indicate a short pulse which counts as 10. There is a long pause after which time the code will be redisplayed.

A code displayed doesn't necessarily mean that the sensor described is faulty. It could also be caused by a bad connector, loose wiring or a defective ECU. The possible error codes are summarizes in the list below. 'S' indicates a short pulse (about 1/2 sec), 'L' indicates a long pulse (about 1 sec), 'P' indicates the pause (about 2 sec) between the cycles, and '...' indicates repetition

Code 01 - Crank angle sensor
DCC1: S P .... (1 short light... long pause ... repeat),
DCC2: does not light.
Fail-safe mode: There is no fail-safe mode for this sensor.

Code 02 - Air flow meter.
DCC1: SS P ... (2 short lights... long pause ... repeat)
DCC2: does not light
Fail-safe mode: Maintains basic signal at preset level.

Code 03 - Water thermo sensor.
DCC1: SSS P .... (3 short lights... long pause ... repeat)
DCC2: does not light
Fail-safe mode: Maintains a constant 80 degree C command.
Comments: this is the two-wire sensor on the back of the thermostat housing

Code 04 - Intake air temp sensor.
DCC1: SSSS P .... (4 short lights... long pause ... repeat)
DCC2: does not light
Fail-safe mode: Maintains constant 20 degree C command.
Comments: This sensor is built into the air flow meter.

Code 05 - Oxygen (O2) sensor.
DCC1: L P.... (1 long light... long pause ... repeat)
DCC2: does not light
Fail-safe mode: The ECU stops feedback correction (open loop operation)
Comments: This sensor is located on the down-pipe / pre-cat.

Code 06 - Throttle sensor.
DCC1: LS P ... (1 long light ... 1 short light ... long pause ... repeat)
DCC2: does not light
Fail-safe mode: The ECU assumes 100% throttle position.
Comments: This is the TPS and it is located underneath the intercooler.

Code 07 - Boost/Pressure sensor.
DCC1: LSS P ... (1 long light ... 2 short lights ... long pause ... repeat)
DCC2: does not light
Fail-safe mode: Maintains constant command: 96 mm Hg (boost sensor), 26.3 kPa (pressure sensor)
Comments: This is located on the right shock tower.

Code 09 - Atmospheric Pressure sensor.
DCC1: LSSSS P ... (1 long light ... 4 short lights ... long pause ... repeat)
DCC2: does not light
Fail-safe mode: Maintains constant sea-level command (boost sensor)
Comments: This is located next to the ECU.

Code 12 - Trailing side coil failure.
DCC1: SS P ... (2 short lights ... long pause ... repeat)
DCC2: S P ... (1 short light ... long pause ... repeat)
Fail-safe mode: Stops operation of trailing side ignition
Comments: indicates a failure within the trailing side ignition system.

Code 15 - Intake air temperature sensor.
DCC1:L P ... (1 long light ... long pause ... repeat)
DCC2: S P ... (1 short light ... long pause ... repeat)
Fail-safe mode: Maintains constant 20C (68F) command.
Comments: This is located on the intake air pipe just prior to the throttle body.

The page that this info came from says that there could be more codes so If any of the GURUs know more then they'll post it up.

85rx-7gsl-se · 04-03-2008, 10:52 PM

Great addition for the site, good work Phoenix.

cool_as_crap · 04-04-2008, 09:28 AM

Wow that's awesome, I'm going to try this.

Phoenix7 · 04-04-2008, 11:56 AM

I have to cut out sections of the FSM so I can add the TPS testing procedure. I am leaving for work so maybe tonight or this weekend.

Phoenix7 · 04-04-2008, 12:31 PM

Also, It's mentioned that you can create longer wires and permanently mount it in the cabin. You drive along and the lights will be off. If an error occurs the lights will blink and you'll know at the same time the ECU knows. I thought it was a nifty idea.

Phoenix7 · 04-04-2008, 07:25 PM

Some people don't like this method and claim it to be unreliable but it's in the FSM for a reason.

I like the multimeter method because you can find dead spots but Figure 7 will show the NA procedure and Figure 8 will show the TII procedure using the LEDs.

See this thread for the Multimeter TPS Testing Method

Figure 7. S4 and S5 NA LED TPS Procedure.

Figure 8. S4 and S5 TII LED TPS Procedure.

Phoenix7 · 04-07-2008, 07:45 PM

KEYWORDS: TPS*, 3500RPM hesistation, bucking, bucks, stumble, stumbles, DMM, AMM, S4*, S5*, LED*, ECU*, Codes, Diagnostics

04-04-2008, 09:28 AM	#5
cool_as_crap BIIZZZAAAARRRRO Join Date: Feb 2008 Location: Frazier Park, CA iTrader: (0) Posts: 56 Rep Power: 17	Wow that's awesome, I'm going to try this.